Screen-tearing happens if the FPS is faster than your frequency, and V-Sync is disabled.
Screen-tearing does not happen when the FPS is slower than the screen, or V-Sync is on.
V-Sync makes your GFX card wait on the monitor.
Tripple-buffering for GL users can often help. It can also sort out mouse-lag.
Humans can only see a little above 30 FPS.
The illusion of smoothness is down to a balance, rather than just rendering extra frames you never get to see.
The FPS setting in UT does not limit the overall FPS. It is used to limit the effects being used.
If UT is not running as fast as the FPS you set, it will cull effects to speed things up.
You would get the same boost by choosing a lower quality setting, as this it what you are making UT do anyway.
I regularly use up to 30 mutators at a time, with extra monsters and zombies all over the place.
A high FPS is not going to happen
If you want high-speed, you have to kill the niceties and give the PC less to do, not more frames to render.
Common things that kill performance;
1) V-Sync on,
2) Maxing out your Anti-Aliasing and Anisotropic filtering (half of your max is fine). Try it disabled in UT but enabled by your Windows drivers.
3) Over-sized screen-modes (This is a low-polly F.P.S. game, and you wont get more pollys). On massive screen-modes you can disable "AA" as the pixels are so small, jagged edges are almost unnoticeable.
The larger screen-modes are intended for larger monitors, or for design work.
On a 19" 4:3 ratio screen, 1024x768 is adequate. And with a little Anti Aliasing, looks great for fast action games.
4) Reflections (Shiny Surfaces) and shadows. Shiny Surfaces is not on by default. You may want to leave it off for multi-play. The basic blob-shadows in UT are not much drain thankfully, so only bother disabling if you need to.
5) Crappy ATI and intel drivers. Unfortunately the new OpenGL renderer may not be your best option.
With GL, ATI cards sometimes use the system RAM instead of the dedicated GFX RAM. If your PC's RAM is not as fast as the RAM on your card, then you will lose performance.
Use a tool like "ATI Tray Tools" to overlay your GFX RAM info. Play UT and see if you still have all your GFX RAM free.
intel OpenGL runs in software mode for most things. Tough-luck. It can do it, but it wont !
To see the difference, you can bypass intel's blocking of Hardware GL for GL screen-savers, by doing something very stupidly simple
Change the file-extension from *.scr to something like *.sCr *.Scr etc. just mix the case of the letters, and you will fool intel.
Try it with some complex 3D eye-candy like the RealySlickScreensavers
http://www.reallyslick.com (Sky Rocket also uses OpenAL for surround-sound)