Are NIMH rechargeable batteries any good?

[teddyFBI]

I have a Rayovac charger and batteries I bought around 4 years ago -- the batteries suck now...i pop a fully charged one into my MP3 player when i go to the gym, and it often dies before I get back home again 2 hrs later. New standard batteries typically give me 10 - 14 hours of playtime.

Is this because I have drained and then recharged the batteries so many times now? Or was the technology really primitive 4 years ago, and have they improved on it at all in the newer chargers / NIMH batteries??