I have a lot of these 18650 lithium-polymer cells, all different, purchased at different occasions with flashlights, headlamps, bike lights etc. Last week I did a test-drive for all types of cells I own with a charge-discharge-charge test. Note that, albeit in use, a single charge will last for a long time (in flashlights I mean) - up to a week, so even the most used cells were used maximum 50 cycles.
So, the results were discouraging. At first, most of these "ultra-something" cells have giant internal impendance - up to one ohm on the worst samples, 0.5 ohms usually. This means very low discharge and charge rates. For example, if you suck one ampere from such a cell, e.g. 3.7 watts, about 0.5 of them (14%) will be spent just to heat the cell. Another bad news is that their real capacity is usually twice lower than declared. Even that I have tested them at 0.1C discharge rate. Some cells had just 500mah capacity (while were declared as 2400). Most were 1000-1400mah. So, about the energy density of the "fake A123" yellow 18650's, but with a much higher internal impendance. Eek.
The best cells that I own were from a ebay seller (don't remember his nick on ebay) that were declared from the beginning as 2200mah. And - surprise - they were for real 2200mah (well, 2150 and such, but meh). They weren't "ultra-anything", they just have a paper label sticked on the cell body.
The resume is: I would never use these cells for a e-bike battery. The best of them (those marked 2200) are very good for flashlights and such, but not for serious loads.
If somebody is interested, I may post a photo of the cells I tested, with their real capacity.