I was not aware of this. This is some hot sexy $hit that I will be hitting hard. Does it level up your weapons too? Please say yes.... I want to snipe from rooftops with shotguns too.
Yes, I levelled up like normal. You take all your classes with you, there's some minor tweaks to perks. Don't know if challenges also go with you, I doubt it.
We played the 2nd mission and got stuck outside the walls of the base unable to move in for the torrent of baddies coming out. The AI spawn and run out of the base, eventually you'll go down but I was mowing them down and I think a coordinated team could sit there all day.
You get less XP per kill compared to a player in MP mode (I think 10XP?). I am no 'pro farmer' but I found myself racking up the XP - we wanted to move in and complete the mission but the non-stop enemies meant we couldn't even take a breather.
Spec ops would be infinitely better with fewer enemies and no XP.