Yeesh. I've been following the last couple of these threads, and the big problem here is that there are too many issues being discussed at once. I think if discussion were broken up like this, we'd all be a lot happier:
1) Refresh rate and LCDs. Since LCD screens don't redraw the same way that CRT monitors do, they don't have a "refresh rate" but rather a per-pixel "response time", which is how long it takes for a pixel to go from black to white and back (or vice versa). While LCD monitors have (generally) a worse "refresh rate" than CRTs (the best LCDs have a 16ms *average* response time, or just over 60Hz, and most have 25-35ms -- a bit over 30Hz), they
*do not flicker at all*. Some people are very annoyed by CRT flicker at 60Hz, a problem which is compounded under fluorescent lighting (which also flickers at 60Hz). I notice 60Hz flicker if I look for it (look at the screen out of the corner of your eye and you'll see it) or if I work in front of one for a long time, though 75Hz and higher doesn't seem to bother me. Rather than flickering, low-speed LCD displays will blur whenever the image on the screen is changing rapidly (as when watching DVD movies or playing games). Tolerance for blur relative to flicker seems to be an individual preference.
2) VSYNC and/or high frame rates. VSYNC makes the graphics card only redraw the screen between refresh cycles. Without VSYNC, you can (and will) get situations where monitor redraws half the screen, but then the video card changes to the next frame -- so you get part of one frame and part of another. This creates visible artifacts ('texture tearing' in particular) during fast motion, and I don't like it. Other people don't notice it as much, and AA can help to cover it up by making the transition less sharp. Whether or not VSYNC is on,
*there is no advantage to having a fps count higher than your monitor's refresh rate/response time* (as long as the minimum never drops below the refresh rate, that is). 150fps@60Hz looks exactly like 100fps@60Hz and 60fps@60Hz (except that without VSYNC you may get even worse tearing due to multiple frame buffer redraws during each monitor refresh). Ideally, you'd have a system capable of running at or higher than your refresh rate at all times, and run with VSYNC enabled (which would lock you to running at, say, 75fps@75Hz).
3) "Choppiness" / "Jitter" / "Lag". There are two different problems being addressed by at least three different names here. One is having a "low" frame rate (with low being a relative term) all the time. The other is having a low frame rate some of the time, or having one that bounces rapidly back and forth between, say, 10-20fps and 60fps (often seen in FPS games where there are extreme peaks and valleys in the number of polygons/textures/effects being rendered). I reserve the term "lag" for network transmission delays, so I would suggest that the first issue be called "choppiness" (or, alternatively, "your graphics card blows") and the second "jitter" or "stutter" (or "your processor/memory/HD blows"/"your graphics card only kind of blows"), just for some sort of cohesiveness in any further discussion. Some people don't mind a fairly low framerate as long as it's constant, while others just can't stand anything below a certain fps number.
4) How many fps are necessary? We've all heard the argument that you can't discern more than 24 FPS. It's crap. Movies and TV run at 24fps (for the most part -- cheap Saturday morning cartoons are usually down in the teens somewhere, for example), but they benefit greatly from the free "antialiasing" (ie, blur) provided by television screens. You ever watch TV (like a football game or something) on a computer monitor? It looks terrible. DVD movies look better because of the increased resolution and the fact that you're not usually getting the same sort of rapid full-screen motion that games give. I guarantee that if you had someone watch, side-by-side, something running (a game loop, for instance) at 20, 30, and 60 fps, they'd be able to tell them apart and would prefer the faster ones. It would be an interesting perceptual psychology experiment, for anyone in college... That said, most people seem to be fine with framerates in the 20s-30s, as long as they don't dip below that too much (which usually means a "resting"/average framerate up in the 50-60s at least).
I hope that helped.