NiMH need a lot less care than NiCad's; don't have that dreaded memory effect, either.
That said, there are a couple of things to avoid with NiMH cells: Heat and Shock. Drop a cell on concrete (or other hard surface), and it's quite likely to be damaged. Allow a "fast" charger to overheat it, and ditto. They also don't like to be run down to nothing.
In some cases, a full (or nearly full) discharge, followed by a slow charge will recondition the cells; in other cases, toss them and replace. A pulse load tester goes a long ways in weeding out good from bad. One such tester is here: http://www.thomas-distributing.com/z...ery-tester.htm
The one thing you need to watch in NiMH vs alkaline is the cell voltage: Alkalines are typically a tad over 1.5V, NiMH (and NiCad's) are somewhere right around 1.2V. Some equipment will run fine on the 3V alkalines provide, but refuse to run on 2.4V.
That said, most late build NiMH cells will far outlast alkalines in use; but are not for long-term emergency equipment. NiMH cells self-discharge at a rate of about 10%/month (as I recall), so if you pop them in your handheld VHF, and throw that in your console for a few months, well, you're going to be doing a lot of talking to yourself when you need help.