I'm seeing about double the WU times on my old P3 (11 hours to 24) and about 50% longer on my (Intel) Mac Mini (~2 hours to ~3.25). I've not tried a P4 yet, but I found that the one thing my old Prestonia Xeon was good at was SETI. It's not keen on Folding (down to two clients throttled to 90% CPU right now), and I guess it'll not like SETI Enhanced much either given the above.
An optimised SETI Enhanced client might help I suppose (they do already exist), although I'm not sure what affect that will have on the credit scoring (in theory I'd expect to score the same for faster completion, which is pretty much the exact opposite of what happened previously). I get the impression this new scoring is contrary to the original Cobblestone concept, but whatever.
Sounds like Einstein might be the way to go for me. Predictor and LHC just plain suck, and folding seems to have lost it's interest since the demise of the 600-pointers and QMDs.
I really don't want to see people leave DC (hell, we've lost a hell of a lot of good crunchers since BOINC happened), but with what's going on in the DC world these days, I'm not entirely surprised. Never thought I'd be considering quitting SETI for good, that's for sure. Mind you, I suspect I might have said the same six months or even a year ago, and I'm still here, just about.