I have had my kGo (from hoosierecigsupply) since I started a few months ago. One went bad and he replaced it right away.
I like that they last all day and night. I now have a VV mod, but still use the SLB 1100 mAh kGo every day. It really kicks with Boge LR and SmokTech dual coils. Great battery life, sleek design.
I will probably get the E-Power 18650 when hoosier gets them in (hopefully next week). But I would say every body would be happy with the kGo. 4.2+ volts off the charger. 3.9 volts under load. Where my eGo is stuck at 3.4.