I have 2 airplanes running 6v NIMH cells and 1 6v nicad and they all do great unregulated. The high surface charge (normally around 7.2) will scrub down to about 6.5 with load, after only a few minutes of operation. Even the aa pack carries 1650 ma(nimh) so you have power to spare in most instances. I have noticed they seem to self discharge a little faster than nicad while sitting. Nothing wrong with regulation if your looking for that perfect unchanging setup, but I prefer the KISS principle
(keep it simple stupid)