There were, and still are, plenty of reasons both to jailbreak an iPhone and root an Android: both options open up the OS to a ton of sweet homebrew features and functionality (I'm not talking about pirating at all). I don't think getting it unlocked from AT&T was even half the reasoning for jailbreaking back then, honestly. Windows Phone is a different story though... barely any features get added. There were still only a very limited number of extra things that Jaxbot of Windows Phone Hacker could do for a WP7 interop unlocked ("jailbroken") device. Most everything that you could do could be done on WP7 with a dev unlocked device. No jailbreaking required.I don't get it... Why do you have to jailbreak your phone at all?? I mean, I get the reasoning behind it back when the iPhone was only available through AT&T and it was locked to that carrier, but really? I would never even attempt to do it, nor would I want to. Why compromise your phone like that? :-/
I'll personally never go down this path until someone figures out how to ACTUALLY add functionality, such as separate volume controls, system-wide orientation lock, and associating filetypes with 3rd party apps (i.e. I would prefer it if my browser links would open in UC Browser, my prefer WP browser).