I agree, iTunes on Windows is a slow piece of shit, that really shouldn't be using OS X UI elements at all, but built as a Windows application and adopt whatever Windows design concessions there are, good or bad. I understand WHY Apple built it like they did, but it's obviously not performing as great as it could.
That said, iTunes doesn't just play mp3's. It burns discs, plays videos, podcasts, audiobooks, has an intelligent suggestion system, internet radio, tv shows, cell phone manager/syncher/application manager/backup manager, shared media player, complete media store, parental restriction system, media server and so on and so on.
True, a lot of people won't use half those features, but to complain that a 'mp3 manager' should run better, well, it's a bit more complex than that. iTunes is a huge, complex piece of software. Yes, it should run way better on Windows (I find it's OS X performance to be pretty great).
If you aren't happy with the way it works, and you keep buying iPods, then it's your own stupid fault and deserve no pity. It might be slow, and it might have niggles that you don't like, but it's not broken, and if you keep buying regardless, then shame on you.
There is other software out there that can manage your iPod and music for you, go and use those if iTunes is so bad. I've tried a few out, but find them to be lacking in design and features.
Sure, Apple try and encrypt the database on your iPod to prevent this happening, but you can understand why. iTunes Music Store.