While to this day eLeaf claims that the majority (if not ALL) the issues with the iStick50 were with clones of the device, most major brands seem to be fairly safe.
The statistics above about charging don't go into detail about the type or brand of devices however the cheaper the knock-off, (or complete off no-name brand) the more likely that the EXACT charger and/or cord is REQUIRED to charge their devices even remotely safely. Hence the old devices that were charged via the 510 could not be mixed and matched.
I think it is rather safe to assume that most 'on board charging' is at a lower rate and lower end voltage than a dedicated charger for these very reasons - they need to be conservative with their charging as they don't know WHAT quality battery the consumer has installed.
Generally, if there is on-board-charging available I'll use it. Much like others I have a extra USB cord right next to where I charge my cell phone overnight.