PlanetUnreal has more information about optimizing Unreal on your machine. I haven't played it yet, and the reports I get are conflicting and heavily biased. All the reviewers seem to care about is how Unreal compares to Quake 2. Which is something like comparing Quake 2 to Quake or even Chasm. So instead of reviewing Unreal, today I will review Quake2 and compare it to Quake.
Quake is fast and has low system requirements.
Quake 2, on the other hand, does not run quite as fast on most systems. If pure framerates are what you crave, Classic Quake with Scitech Display Doctor is about as smooth as you can get. Quake 2 has beautiful and varied level designs. Quake really doesn't compare, it's levels are nice for their time but pretty monotonous. Quake 2 also has some very nice models, but alas, most of them are boring humanoids that could have came out of any of the Star Trek spin-off TV shows or movies.