It's like iOS but without the ability to jailbreak.
No root or custom ROMs, as far as I know.
WP is locked down pretty well. You won't find a bigger fan of it than me, but if you like rooting, ROMing, and heavily customizing with launchers and such, keep Android. Windows Phone isn't like its predecessor, Windows Mobile, which pretty much ushered in the mobile rooting/ROMing scene long before Android came out.
I use both Windows Phone and Android on a daily basis.