wut! I had an inverted opinion - I thought the SP was alright but lacked some of the polish of the original, but the MP was excellent. CODUO is still one of my top-tier favorite MP games. I don't know what you mean by the vehicles being scarce, maybe you didn't give the right maps enough play time
About developers, I think it's often difficult for an outside dev to nail the same tone and feel of a game in an expansion, and it shows.