Same, I have a pretty heavy duty machine and it still happens. Until the engine decouples graphics from the physics, this game will always lag.

If by 'the fps thing' you mean CPU smoothing, yes, it's on. I'm not quite that dumb.

Same here, right when i turn auto-FPS keeper/game slower(realtime decoupler) on, it drops the game speed to 70-80% (AMD athlon 64 4000+). Adjusting the "real to sim cap" setting with 3-4 keys to about 20-30 ms, and turning the realtime decoupler off seems to make the game very smooth, however the threshold is very small and it easily gets jerky.

I think build 20 was as smooth as B21 without decoupler on (but slightly slower), however B21 seems to easily get either too jerky or too slow. Controlling ships feels like you were at top speed in B20 and then this skipping started, in B21 it's always like that when the game gets jerky, so i have to constantly tweak the "real to sim cap" and turn the realtime decoupler on and off all the time when i want better control when flying actors or ships.

I almost thought the slow-motion ruined the game, then I realized the jaw-dropping effect it had on gameplay.

I actually won a map I made and never released, that was unwinnable because of the hidden nukes in the ceiling.

I get the fullspeed sounds all the time unless I'm actively using the ypsilon or somesuch. And my computer's a three-year-old POS.

I like it, and I like how the music slows down too, but the slow motion you get for every gib is annoying.
I wish Data would just bite the bullet and make it use your graphics card. Lazy bugger.