Thanks to my mate Brum, I got into the Alpha last night. Was on call last night so only managed a couple of hours, but it looked promising. Lots of texture, lots of detail, but I did feel the art style was bordering on (no pun intended) Borderlands at times, which is not my favourite look to be honest.
The handling is ok. I would have preferred a lot less weight to turning, but it's still early days. I've never played Halo so it may be comparable in terms of other Bungie games, I wouldn't know. The MMO element seems reasonably simple without too many options, which is good as this is still fundamentally a shooter, not a dungeon crawl. The AI was fairly solid too although the first underground "Boss" type character was impossible to bring down alone, especially with the weapons and special abilities on offer when levelled up to 4. But it without doubt feels like a shooter, not a compromise.
I have the feeling it will perform best in co op mode (I know, here he goes on about co op again! ). But after a couple of public events that was my impression. There is a pvp area with performance challenges that I haven't tried (and probably won't). You can also have and manage multiple characters which is cool if you don't want to stick with one class. The control and upgrade menu is also nice and very clearly laid out, unlike the cluttered Watchdogs effort.
Overall I was quite impressed and want to try to get a few hours in today and tonight after the footy.