I fail to see the point in jail breaking, it just seems to be something to do to prove your l337 h4ck1ng sk1lz; I’m pretty sure that there’s an app in the app store that will do anything you could reasonably want, without needing to jailbreak.
You don’t need to jailbreak to unlock the phone, either.
As far as iTunes is concerned, I’ve yet to see anyone come up with a convincing argument against it, it’s usually down to ‘well, I don’t like it, it’s crap, innit!’, which is hardly convincing. It works perfectly for me, and has done for years, and the fact that I can easily control how I play my music through my a/v system from my Mac mini via Remote on my pad or phone pleases me immensely.
You can rip your music in MP3 or AAC+, which is MP4 by another name, and is NOT a proprietary format; it will play on Nokia and Sony phones, among others, and music ripped at 320Kb is superb quality.