IMO, the Russian's shouldn't be undertaking new military projects while they still exist in the mafia nationalist undertow aftermath of the communist period. I guess this is what happens when the West steps in and revitalizes the national petrogas industry, only to see it 'nationalized' a few years later.
That said, the Pak FA is not perfect but it is interesting. The YF-23 was guaranteed to fail with the butterfly tails, simply not enough separation of directional and pitch/roll authority necessary for a fighter. The production/EMD F-23 would have looked a lot like what you see here. Which is itself a shame because it indicates that Russia continues to play the catchup game rather than attempting to chart a new mission with a new design that is truly an indigenously unique undertaking. That said, they remain too short IMO and will be subject to blanking because of it. There may also be issues with the root-vent scoops and vortices off the squared off inlet tops.
That said, I see a lot of features that don't make much sense to me at the moment. The conventional IRST bulb, the fastener dotted fuselage panels, the large gaps in the underside fuselage/wing fairings etc. etc. All point to a minimalist approach to VLO rather than an 'as we now know it to be' (EOTS facetted fairing etc.) condtion.
The rear fuselage looks likely to have boat tail issues to me. The implied thickness of the weapons bay area running too far aft and being entirely too squared off.
I also question the utility of this jet as it seems likely that it is compromised as a multirole platform by the narrowness of the inlet:inlet distance across the weapons bays. The YF-23 tried to get away with this by promising a fuselage extension and nested AAMs on a bay that 'looked like a Lancaster'. But I don't think that this will prove practical for even a generation of Russian GBU-38/39 clones and certainly not for JDAM class munitions. As the politics of mixed fleets still prevails (with a lone exception in Malaysia) an A2A dedicated platform may be deemed too restrictive for much the same (albeit mistaken) reasons the F-22 was.
The inlets are broad (which could lead to mixed compression 'shock burp' issues) but shallow and I see a lot of potential for boundary layer choking around the upper rim. The canopy has the look of an F-35 as much as an F-23 and without DAS like surround vision I doubt if all round visibility is going to be good. Which is not to say it won't likely be an improvment on previous Soviet types!

Ironic, with that much downslope on the nose, it looks like it's got some carrier suitability drivers until you see how long that stinger is and how nose-low the stance is going to slam to.
Wings look small, likely as a result of the immense spanwise distribution of the fuselage area but are further compromised by being shoved back so far and swept so much. The first will impact stab authorities. The second will likely result in a higher cruise Mach but only with additive compromises in center of lift shift and overall higher wingloading.
Nice big, high flotation, gear. Not always a good thing when it's so widely spread apart as you can get a tippy toe effect if the wing doesn't dump lift in the ground effect and of course there is also a large structural reinforcement penalty on carry through from both sides of the fuselage:wings mating joints. Haven't seen the actual nose gear retraction sequence but even if it folds forward, that large extension strut pushes back the NLG intrustion on the weapons bay quite a bit.
In combination with the tail-up stance and the relatively short longitudinal wheelbase, we could be seeing some significant issues with the weapons bay loading CGs. You're certainly going to have to be careful in the way you bring the jet in.
OVERALL:
Bound to be an expensive jet. Easily in the 100 million dollar range. They would have been better off sticking with the original concept art which showed a lot of preference for single engine (or SE adaptable) configurations. Where price becomes a dominant factor is in basing coverage of the still broad Russian territories vs. sortie generation by airforces which, even if they swallow the stealth bullet whole, have to wonder at the efficacy of a 20 jet airforce with no strike capability to speak of vs. what a couple hundred S-400 or a couple thousand drones could buy them.
If the combined 'expeditionary' force model continues to consist of 200-400 jets, 20 jets will simply be run over in the turn and run out of missiles by standoff munitions and cruise which keeps them from effectively seeing equivalent LO shooters lobbing X8 SDBs from 60+nm.
OTOH, if you want an INNOVATIVE look at the future of 'fighter design' here are your two best bets-
ABL-1 testfire against Minuteman
http://www.youtube.com/watch?v=mq7ieXNoyVw&feature=related
Mirach target drone launch
http://www.vectorsite.net/twuav_03_07.jpg
The ABL, before technical details were obscured, was stated in AvLeak as having a range so great that _airliner and satellites behind the target_ had to be deconflicted before firing. That's not a 250km weapon system folks. That's not even a 400km weapon. That's a line of sight weapon on something moving as slow as a jet aircraft rather than as fast as a rotating, mirror bright, ICBM with quick burn motors designed to put it out of range in seconds.
Anyone who has graduated lead in fighter training knows how utterly outclassed they are as a knight of the sky by a simple unmanned jet whose construction is possible for any nation with basic aviation maintenance repair skills from business jet level on up. They are 4-5 times more maneuverable than any fighter. They are at least an order of magnitude more difficult to acquire (which is why so many miss-iles 'miss' in tests when the angle off exceeds what the signature augmentation can cover) and they are are DIRT CHEAP to build. As we have also known since about the 1930s when we first started using them. They also have two other advantages: As shown, they can be fired by catapult or rocket from the back of a simple trailer and are equally recoverable by parachute anywhere you care to put a beacon at the end of a simple (astro inertial if you're afraid of GPS loss) autopilot run. They are also vastly more capable than even the best of the telephone pole class weapons like the S-300/400/ERINT/ASTER. Why? Because the big SAMs cannot lock onto stealth targets at anything approaching their maximum range while, true to form for a 'miss-ile' they expend all their propellant impulse in a single great rush to make up the fleeting TIME difference before the target again vanishes at perhaps WEZ = .5 of total kinematic performance. OTOH, a 6ft long MALI could fly a legitimate 230nm in the course of a 20 minute flight profile _already at altitude and airspeed_, then sit there for 10 minutes waiting for the threat to come buy, fresh off the pre-target tanker and heavy with gas and bombs. Miss once come around again for another taran pass.
And such an hybrid missile/air vehicle could be bought in the hundreds if not _thousands_ of shots per raid. As the ultimate Zaum Sau/Wilde Sau combined free hunt sweep and point defense controlled intercept force, they would be unbeatable by stealth alone because a pack of them could sweep HUNDREDS of cubic miles per minute using linked EO seeker that emitted nothing.
All at a fraction of what yesterday's _mission solution_ PAK-FA will cost.
And every fighter pilot knows it because they have faced them in exercises and been humiliated by drone operators whose sole view of the world is a front facing camera. For 50 years.
As does every aviation manufacturer that has been building target and/or recce drones for the same period-
http://www.youtube.com/watch?v=RmysvZ2VfAA
(ATARS) BQM-154 or Reis D with gear anyone?
_NEVER_ copy **the way** the enemy does something. You will always be playing second best catchup on something they have already mastered.
GLAR