To chime in on this clever vs waffle thing...
I, too, get ~15% rejects to clever (even with server ping of 50) and less than 1% on waffle. It was my understanding that the profitability figures on each site are for accepted mhash/sec (read in their forums) so for me it was no contest who to choose. EDIT: (waffle)
+1 for me. <10ms ping from useast server for me +2% rejects. Out of 5mhs, I get about 4.5 accepted on waffle and about 3.5 on clever. No contest. Wafflepool for me for now.