If the nicads will still cycle OK, there's really nothing wrong with them? If you want new and you're going to stay on the smaller side of 120 generally, you could go with nimh. The bigger stuff, that's looking high torque and metal gears, I think LiFe/A123 (same thing, but not to be confused with LiPo) are a better plan.

Here some reading if you'd like some help coming up to speed on the new stuff. No association with the company, just steering you to somebody that's put a lot to think about in print. Put a lot of "stuff" into much clearer focus for me!

http://www.hangtimes.com/weightcompare.html

http://www.hangtimes.com/a123rxsetup.html

http://www.hangtimes.com/a123_batter...iants_faq.html