I have all three types in 510. kGo 1100 is awesome. Riva 750mAh has not given me any problems. The eGo 650mAh seems a little weak, as it is metered to 3.4v. The kGo and RIVA hit 4.2+ at full charge, and slowly creep down towards 3.7 as they drain.
I use same chargers, cartos, attys and cones with all three.