Just tested the beta and 'gold' version on my old pc. Its specs are:
AMD Athlon 3500+ 2.2 Ghz
Windows XP Home SP2
1 Gb RAM
ATI X800 XT PE 256Mb
So a pretty top end pc for 3 years ago, and I'd say a pretty average pc now, so should easily be able to run a moving blocks game.
Don't have actual benchmarks, but I'm sure the feeling of the game 'catching up' is caused by drastic changes in the frame rate, eg 50 to 30 in 1 second.
The gold version felt pretty smooth, although FRAPS reported a constant 30 fps, but it did drop below 25 a few times, causing serious lag.
On the Beta, felt MUCH better, getting steady 50+ fps at 1280x1024, and much smoother, this is all done using enhanced, as premium just mucks up the frame rate and makes the game look blurry, which I personally don't like anyway

I think I've found an interesting clue actually. If the menu system runs at 60 fps or close, I'm pretty damn sure the real game will run well too, as before my fix, the 'gold' edition chugged on the menus and lagged in game, and now it runs at 60 fps. Same for my old comp. The beta's menus are fine, but the gold edition lags a lot. This might help the devs track down the cause of the lag?
As for potential fixes, i installed hotfixes for Vista (don't think it did anything), installed different drivers, and added a profile for QuestViewer.exe (found in steamapps-common-engine) to turn off SLI but maybe it helped? Ill run some more tests...
