So who's using it ?
We all know a great many people have been suffering from performance issues, a dire circumstance indeed. In order to relieve themselves, and others, of these issues some enterprising chaps have figured out a way of increasing performance. As if by arcane wizardry this .dll allegedly improves the framerate without any negative consequences in terms image quality. As evidenced by the amount of support these .dll fixes are garnering all over the glorious landscape of the internet.
Evidence viewable here:
http://www.thenexusforums.com/index.php?/topic/249135-d3d9-perf-fix-endorsemants
http://www.evga.com/forums/tm.aspx?high=&m=641225&mpage=1#644658
http://forums.steampowered.com/forums/showthread.php?p=17956558
And I will stop here, however the list of threads and single posts, of users who have been helped by some version of this miraculous d3d9.dll, goes on virtually forever. However some have voiced entirely understandable concerns about using a .dll file, that you got from some unsavory internet fellows, on your personal computer in this day and age of virtual identity thievery and other such malfeasance A well known editor on a tweaking website has even spoken out against the use of this .dll.
View that here: http://www.tweakguides.com/ (scroll down to 27, october).
User Sfade weighs in on the trustworthyness of his advice in this matter.
A word on that particular segment in your post, and of course this is purely my personal opinion - take it for what it is worth to you:
While that particular website does have a lot of good links to useful utilities and such, his advice and frequently voluminous opinions misrepresented as 'fact' are woefully myopic and spread a great deal of misinformation as a result of blatant ignorance and even refusal to actually investigate and/or research that which he proceeds to criticize. I'm not going to go into details but that individual has gotten himself banned from various forums as a result of his behavior and inability to behave in a civil manner, since witnessing those events the dubious credibility of tweakguides declined to pratically infinitesimal. As I said though, it is a decent place for links to utilities and news (from generally credible sources) - but I would call into serious question the validity of anything that comes as personal advice from that site.
Bethesda has also stated that they do not recommend using files downloaded from the internet. And others yet have claimed that the increased framerates are a direct result of this .dll lowering the image quality in the background Proof for this was, however, hard to find to the people using the .dll. Furthermore noone seems to certain as to how the d3d9.dll affects Fallout:NV or the operating system to achieve these miraculous results, people have speculated however noone has posted definitive proof that I have been able to find.
They say the fix makes fallout NV render in d3d9 on windows 7 machines. The fix apparently also interacts with FaceGen to achieve the results it does. I have also heard claims that it loads the correct shader set for your videocard. And finally some say it lowers the image quality to achieve an increase in fps. By whichever method this operates is a question that needs to be answered and it would seem prudent for Bethesda to take a look into it, if only for the claims of increased performance.
And a few questions:
Are you using the fix: Yes/No
Windows 7/Video card: Yes/No - Brand - Type (like so ATI - HD5870)
Increased performance: Yes/No
Image Quality Issues: Yes/No
Quality Settings: Low --> Ultra - 2x 4x 8x AA? - 1 -> 16x af ?
Why are you using/not using the fix ?
Special Question( I'm giving away a gifted steam copy of the new A vs P game to the person with the correct answer)
Do you know how/why it works, can you prove it ? if so post it here(mail it to them) so bethesda can get a patch out to help people affected that don't know about the fix.
I have made this topic to expand on my findings, it explains why and how the d3d9.dll works. http://www.gamesas.com/index.php?/topic/1134379-d3d9dll-and-why-it-works/.