i am actually liking android (ice cream sandwich) a lot. in a lot of ways, i prefer it to ios 5, and i'd pick it over the ipad 2 just for the os. i'd call it a good competitor, and at 100 dollars less than the ipad (32gb) it is a surprisingly good deal (assuming you can find one).
i don't know enough about windows 8. maybe it will be good, but it's hard for me to get too excited about it. i wonder what they will offer that ics and ios don't. maybe just the office apps?
as for the prime, i am still on the fence about the tf201. i'm pretty pleased with it overall, but as i mentioned in another thread, there are some niggles. will the tf700t be ok with higher resolution, the same processor, and a higher price than the ipad? i kind of doubt it.
ics is a good competitor. there are finally a lot of great apps in the marketplace. the marketplace is much more open than apple's, so i can find some great stuff that i'll never see in itunes. but, when it comes to the devices, i think the ipad 3 (assuming it has what i think it will, and assuming the price is the same) will be stiff competition for another year.
by the way, there will be some androids, some apples, and some windows who will never consider competitors to be any good. stepping beyond our own idosyncratic needs, i think there is plenty of room out there for different approaches. there is certainly enough for two, but i do wonder a little about three...