I thought I was getting more than 12/hr when we did some AAs on WCG a while ago, must have remembered incorrectly or perhaps they have dropped it again, it must use a reduce towards zero scheme because I was getting about 12-16 on my old A64 Clawhammer @ 2GHz a few years ago.
Don't know what the highest credit CPU project would be, probably AQUA I suppose. QMC has the highest credit tasks I have experienced in the last 12 months but only on certain beta tasks that are rarely issued. AQUA is too unstable for me when running GPU projects, plus it's a nuisance to configure to use less than all cores so I no longer run it. Next would possibly be the PrimeGrid Sieve tasks, I don't run them anymore either except for Challenges because I already have the badges.
Might give the ATI OpenCL beta a go when ATI fixes the HD 5970 bug. Credit is very poor for a GPU project but it may help the developer to give it a trial for a while.
eOn is going along fine, I had a lockup when I first started but it has been OK since then. I see what you mean about the uploads, I'm only running it on 3 cores and each task has a decent sized upload. If I was running it on 8 cores it would be going to town on the uploads. :)