The mix quality varies wildly on these! A few of the early hits ("Bad Romance", "Just Dance", "LoveGame") have been around as singles for a while and all sound like they were mixed by the same person. I wouldn't say they're spectacular, but an effort was made to craft an immersive experience using all the channels and it's fun hearing the vocals isolated in the center speaker. Dynamics also seem a bit better than the original stereo mixes.
On the other side of the spectrum, you have tracks like "Telephone" and "The Edge Of Glory" that sound like they were run through some kind of unwrap/upmix process. It's basically the stereo mix in front, with some effects and the odd instrument/vocal duplicated at a lower level in the side or rear channels. The center and heights get little-to-no signal.
