After reading up for a couple weeks I ended up buying the Riva (which arrived yesterday, woot!). My reasons were a) $20 cheaper, b) rubber button (I likes rubber buttons), c) 100mAh higher capacity battery, d) at the time I only had PayPal money available and I was ordering from Eastmall who carries Rivas and not eGos.
So far it's working great. Good flavor (more flavor than my KR8), good vapor (on par with KR8 with crappy
juice), and 510 parts are almost everywhere so the replacement parts cost should be virtually identical to that of an eGo.
I believe most every lithium battery is limited to somewhere around 300 recharges before rechargeability starts to degrade. I'm not an expert on batteries though, so I could easily be mistaken.