I found an old iPod mini that I hadn't used in years and gave it a shot. Everything was good for a solid week when all of a sudden, boom, iPod crashed and I lost all music.
Most recently I found my old 160GB iPod Classic and it lags very bad and freezes quite often. I don't think I'll be using it in near future, probably going to stick to the iPhone.
I'd say the problem lies in using HDD based MP3 players.