Ok, so initial reactions time:
-Spartan Ops? Yes please! It sounds like it could be really fun, and seems to imply new content gets released as time goes on.. Possibly an ongoing story? =)
-No firefight? Damn, that is a loss, but I will admit I liked ODSTs a ton and really didn't feel the variation in Reach. Poor Ghaleon. =(
-Customizable starting weapons? Hell, Ill take it as long as you can't start with power weapons.. in fact, I guessed at something like this happening. As long as the choices are weapons like AR, BR, DMR, etc and not Sniper, shotgun, rockets etc. Im pretty accepting of this change, it sounds fun.
-Seems to mention a weapon called assualt carbine, I wonder what that is. (It also mentions the AR and Carbine Rifle so its not those)
-Also, something tells me Halo 4 will have a ton more weapons than past Halo titles. I really can't wait to see what they have cooking, and Im bummed that we weren't shown anything new yet, at least in the leaked scans.
-Sprint as standard? Sure, sounds good to me.
-AAs returning? Yeah, Ill accept it, I hope they are balanced but AAs don't have to be terrible.
-Forerunner vision sounds like it could be fun IF it isn't overpowered.
-No respawn delay? Hm. That doesn't worry me, but Im not particularly excited about it either. Ill accept it.
- Random power weapon drops? Hm. This one gives me mixed feelings, it sounds like it could be really cool, but I hope some things will still spawn at consistent spots like the shotgun, with more powerful weapons doing the random drop. I both like and don't like this one.
-Join in progress games? Yes! And no! I both like and don't like this one, but I think its positives will outweigh its negatives vastly. Bring it on.
-Red vs Blue story sounds cool I wonder if it will tie in with Spartan Ops
-New investment system sounds like a positive change
-New game modes sound nice.
-Visually the SP stuff looks stunning, the MP stuff looks a lot like Reach with better lighting. That Plasma explosion looks kinda meh.
-Cortana. =)
-Assassinations are back. I wonder if they will allow us to unlock weapon specific assassinations such as in Gears 3. =)
I really hope more information will come out soon.. I can't wait for a more detailed write up as I know my magazine will take forever to come in the mail.