There's a gunfight that virtually every player will experience in the first hour of play and for everyone it turned into a slideshow.
The community found a fix within a day or two - a replacement dll - and the next driver from Nvidia fixed it too. So why it wasnt spotted
during testing and Nvidia asked to release a beta driver for it is baffling. That tells you a lot about the 'quality' of this product.
I'm glad you took the time to qualify the statement on performance errors - an unnerving number of people don't bother even putting "virtually" in front of "everyone." But yeah the people who experienced unexpectedly poor performance (most often cited reason appears to be nvidia+facegen) seemed at first to be a random assortment of nvidia users with a wide range of system configurations across multiple OS types. What was really confounding was that some ATI/AMD users were experiencing very similar stuttering and NPC slowdown issues (though they are either fewer or at least less loud.)
The D3d9.dll fix, which fixed a large portion of people's problems instantly and without many problems besides potential endgame cutscene crashing, was actually already out well before this game was even entering development. This made it seem like this had to be the same glitch Nvidia (and primarily windows 7 and vist x64 OS) users had seen even in the final patched version of Fallout 3. Were this the case - that would be quite frustrating.
The odd thing about that fix though is that it is a sort of sledgehammer rather than a scalpel - it acts almost like a directx compatability mode by forcing use of DX9 shaders/settings and spoofing (in a very superficial and relatively problem-free way) an older video card. This masked the reality that though the fix was effectively identical, the problem it addressed was not wholly the same as the one with Fallout 3. At first I took that line of thinking as overly optomistic and giving an excessive benefit of the doubt to Obsidian. That was until I found that my my media server (which has almost identical hardware as my main desktop except for the graphics card being a GTX 265 instead of a GTX 485) ran the game as smooth as butter while my primary gaming rig ran it.. well it was more like that crust that builds up in the bottom of a very old tub of "I Can't Beleive It's Not Butter"; at which point the goop inside the container is so noxious that the label becomes ironic.
Anyways this kind of pissed me off so I started comparing DXDIAG outputs for the systems. The only difference, besides the gaming desktop having a superior graphics card and a more-than-decent SSD, was the driver version. My media sever, which had been my gaming rig a while back, had not had the drivers updated for about a year. Upon updating them to the latest drivers (at launch of the game)... BAM stuttering. It seems that there is at least one Nvidia driver release from quite some time ago that is new enough not to CTD as soon as you launch and also did not have the performance issues with the FaceGen rendering.
So... how could they have caught this particular issue? Well it would not have required significantly more time, unlike more thuroughly running through all the quest variations and engine modifications they made, but would have required significantly more hardware. This issue could have been caught by a straight forward, though admittedly expensive, testbed using a representative sampling of likely hardware configurations AND a range of video driver versions. Most notably - some of the driver versions released within 6 months of the game launch date. Still, part of me can sympathize with the logic behind the assumption that newer drivers (and over many revisions) would react so poorly to the render-er choices made by the game and engine. Ah well I guess it should serve as a lesson that not even game developers should assume patches won't break something that had been previously working - whether or not it's actually accurate to say the patch broke anything as opposed to the driver patches exposed an engine flaw that had previously serendipitously not presented itself.