I think it was a really foolish idea to make this an exclusively 360 game. RTS games have never worked well on the console, and the recent Red Alert 3 was no exception to that.
Thus, there is no way I will purchase this game for the 360! And i know i'm not alone in that opinion. I love halo, i played halo 1 until and a bit past halo 2z release, i purchased XBL when i got Halo 2 because i wanted to experience the full multiplayer, i continued playing Halo 2 until Halo 3z release- at which point i purchased a 360 purely to play Halo 3, and began transfering my account. I got collectors on both Halo 2 and Halo 3. When i heard they were making an RTS, as Halo was originally planned to be, i was PSYCHED! Extremely excited!
Now that i've seen it's never coming to the PC however, I'm horribly disappointed and let down. I understand it is a lot of work to release games to multiple systems, and i understand why since halo started on the 360, it pretty much had to be released to the 360... But I for one, will not purcahse this game for the 360, no matter how amazing the reviews are, because I've never seen a successful RTS and won't waste my money on another attempt, just because it's themed after the best series of shooters I've played.
Without the keyboard/mouse combination, it's slower and more clumsy when selecting units and specifying orders.