Originally Posted by OWA
I think it can increase performance but probably won't do much for performance if they're using it to add more effects. If they just took some PS 2.0 code and rewrote it to use PS 3.0 you might see an increase in performance since PS 3.0 is more efficient. But, a lot of developers may end up using the speed increase to justify adding more effects so in the end the peformance gain may be offset by an increased number of effects. So, it could end up the same speed or slower (but should look better if they went the increased number of effects route). The above is just my interpretation on what I've been reading about it (since I'm definitely not an expert).
the onky situations where ps 3.0 is faster than 2.0 is situations where extremely complex or long shaders are used so that dnyamic flow control and branching benefits actually outweigh the cpu cycles they take. we will not see any games like that thsi generation because they will slow nv40 and r420 to a crawl.