I've played the demo for about 5 minutes... it was ok, it didn't really grab me though.
I'm not a shooter fan. I enjoy video games in general though so some shooters I like but most of them I don't. I'll give them a chance and if it grabs me I'll buy it and play through it, if I have a lot of friends that play it I might get it to play with them. In general though the market is overly flooded with Shooters and most of them are generic junk IMO.
For instance I really liked Time-Splitters 2 on Xbox. It had an interesting story, it was fast paced and had hundreds of weapon, ava, level, and game type options for a really fun multiplayer experience. I also really liked COD2 on the 360 (though I never played it multiplayer and sold it after I beat the game solo). COD2 didn't impress me in the kiosk, when I played the demo at home it really grabbed me and bought it and played through it. Asside from the People on XS I only have 1 friend IRL with COD2 and he wasn't that interested in playing online. So I sold it.
I LOATHE the Halo series... both of them. Though, Halo 1 I can at least tolerate. My friends in college loved the game so I played a lot of it because that was all they ever wanted to play but in general I would have rather played TS2. Halo 2 was complete garbage the level designs were boring, the weapon changes made everything feel generic. Playing online you were either faced with vulgar, racist, pre-pubescent 10 year olds or cheaters.
Not to mention it barely changed from the first one. sure they re-wrote everything from the ground up but they spent all their time and money doing that and forgot to actually add game elements. If it were any other shooter franchise Halo 2 would have been called an EXPANSION PACK. Seriously think about it, they spent three years and pretty much what you got was multi over XBL, dual wielding and a 2nd avatar to choose from.