ORIGINAL: Gray Beard
I have used the regulators and gave up on them when I started using two batteries or the bigger Sub-C battery. As CG mentioned, it was just another item that could go wrong.
One of the local club members lost a very nice jet last year which he eventually determined was caused by a faulty regulator. His solution? Go back to Nicad or NiMh batteries. They do a more good enough job for the application and eliminate a potential failure point.