thus far, smoothness in ICS is definitely a jump over gingerbread.. but it does have hitches and stutters in the app drawer and a few other places..hopefully these will be ironed out, leaving nothing but buttery smoothness all around.
imo, WP 7.5 and iOS are still smoother and have better, more consistent user experiences. ICS shows that Apple and Microsoft can't afford to rest on their laurels, though.. because Google is closing the gap.
Android is a different animal than either of the other two.. and it can be frustrating and intimidating to people who aren't tech savvy. ICS helps by breaking the settings down into meaningful categories.. but there are still a lot of things in there that are intimidating to users that are welcome to more technically proficient folks.. things like the built-in task manager, certificate settings, etc are things that evoke the feeling of a PC more than a device they just use to make phone calls and read an e-mail or two.
ICS is a step in the right direction.. but Google still has more work to do. Definitely the best version of Android, though.
My opinion of ICS may change more as I use my galaxy nexus, but so far I just think it is the best version of android.. and not necessarily superior to WP 7 or iOS.