A couple weeks ago when my review copy first arrived I put some time into single player which so far I find to be very straight-forward and simple yet oddly still enjoyable. Its pretty much a "get from point A to point B" affair, but it manages to do it in a way that's still engaging. You have control over your squad mates with simple commands like "fire at will" and the system is very intuitive when it comes to ordering your squad mates where to go as very rarely do I have to re-issue the command because they walked to the wrong place.
I have yet to try online co-op but I hope to at some point as with any online co-op mode I imagine it makes the single player a much more social and thus a more enjoyable experience.
If there is anything particular that you'd like to know about the game before it's release on Tuesday feel free to ask me in the comments section and I'll be happy to respond.