If it is like the Tec 40, you might try putting aluminum foil in the bottom of the light because the - (negative) end of NiMH batteries often don't stick out far enough to make contact. I had to put aluminum foil in my Tec 40 to make it work with NiMH batteries.
The contacts in the bottom of the light are identical to the Tec 40.
I don't see not being able to use NiMHs in this as a disadvantage. This is due to the long runtime on Alkalines. NiMHs are likely to self discharge before you get max runtime out of it. I see NiMHs in this light as a disadvantage.