MichaelMeissner:
I recall last year in the camera forums, people were shouting about using the new NiZn batteries because it sped up their flash recharge times, and then about 6 months later reality set in, when it became apparent that some/all flashes weren't prepared for the higher voltage. And if you mentioned using NiZn batteries, manufacturers might not honor warranties (Strobist: NiZn Batteries: Long-Term Update).
The new wave NiZn recharagables have some interesting features, and the nominal voltage much closer to alkalines is one of them. However, this does illustrate the point I was making rather well, you have to ensure your device can handle the total voltage of a battery pack at all charge levels. Otherwise it can cause malfunctions and/or damage.