I've only used the accompanying charger on my Grandcells but it's cheap and comes with 12/16/24 packs of batteries. Since the Grandcells aren't NiCd or NiMh, I think their charger is a must ... at least for non-tech types like myself - a good EE could probably dissect a charger and see what so special, if anything. It's just a simple plug-into-the-wall rack that holds 4 cells. Extra chargers are cheap too, I got two my first order.
Regarding usage at higher amp draws, like servo packs or the multi-model TXs, I have to say that I have not used them in those applications. I've only used them in my Fut PEKA fm transmitters (and my wife's elec. toothbrush) and they work great there.
For you guys that got a short life out of 'em, did you ever drain them completely with a bulb discharger? When I first got them, I would use them till my TX showed 'medium' (two lites lit), then recharge them - usually overnight or til the green 'ready' lite came on on their charger. I got 6-8 5 minute heats at 'full charge' when they were new. But after a couple of times doing this, the volts really dropped & the discharge curve was crap; I'd get 1.5V for only a few minutes at best, then 'medium' again for maybe 15-20 minutes of use. Pllfftt on that! So I took the 8 cells, put them in Radio Shack 8-cell battery tray, attached 1 #1157 bulb and drained them. [They wuz hot! LOL], but when I let them cool & charged them again they came back like new. If you haven't pitched them you might give it a try ... [Obligatory Disclaimer: I know this is NOT what the Mfg recommends, and it goes against the "no memory syndrome" claim of the Mfg, and you likely would void any warranty (?), but I just wanted to share what worked for me.]