Performance Issues with 1st and 2nd game, but 3rd game was great
My biggest complaint was the poor frame-rate issues with the first SC and 2nd SC:PT. Overall the graphics was great, but the frame-rate was considerably poor and the whole game jitters after every character dialogue.
The third game however played very well. Verdict is that if you really want to play the trilogy on PS3 (as on the PC you can't play Chaos Theory on Win7); by all means go ahead.