The 18650 def has problems. I have the 14650 and love it and haven't had the slightest problem. Many vendors stopped carrying the 18650 bc of the switch.
If you ever get a 14650, make sure it comes with the plastic button switch and not the rubber one. CCV and Hoosier both have the kit that comes with the plastic button switch.
Te cheapest I've found for a replacement 14650 switch is CCV for $9.50.
For 18650 users, Hoosier has the 5v switch but it will ONLY work if you have the tube with the newer threading. DO NOT buy it if you have the older 18650. It won't work/fit on it.
Personally I would never buy a 18650. Their def not worth it just to have longer battery life. Their problematic and can be a total pain. The 14650 works MUCH better, and the batteries are def no slouch. I use the ressurectors and get about a day to a day and a half on one battery. And it's not like it's hard to carry a spare so I really don't find the 18650 that necessary.
The only thing I found better about the 18650 is that it's easier to get 18650 batteries than 14650 batteries. But it's really not that hard to get 14650 batteries and you can get 14650 hi-drains too. Also getting spare parts for the 18650 is damn near impossible, while getting spare parts for the 14650 is no problem.
So for anyone considering getting an Epower, def get the 14650. I found it can handle any carto/atty i throw at it and works WAY better with LRs than an eGo which can be ruined by using LRs.
I think it's a great PV for the price. All PVs have one problem or another and the 14650s is obviously the occasional switch problem. I haven't had the slightest problem with my switch, but if you think about it, even if you had to replace the switch every month, it's really not that bad. Your not going to have to replace the switch every month, but even if you did, that's $9.50 a month. I used to spend almost that much for a pack of cigs EVERYDAY.
If you think about it like that, then it's actually quite cheap to maintain the 14650 and have a great PV.