If you have played Uncharted for PS3 on a nice HDTV and paid much attention, it is the single most impressive graphics rendering in any game on any platform I have seen - even embarrassing Crysis on the PC, with the shear level of environmental micro-rendered detail and generous raw polygon usage. However, as far as I know, Uncharted is the only game currently released that uses a significant portion of CELL(about 30 percent according to an interview with the publisher), with most games using the mediocre RSX back end GPU only(apparently, it's very easy to progam/use as compared to optimizing for the CELL).
-Chris