Damn. WOW.
For an "unfinished" remix, it's DAMN good! This really pulls some nostalgia on me, since Just Dance was the first Gaga song I ever heard. The twists on the melodies came out very well, and the fact that the vocals were fairly true to the originals also pleased me. (Gaga's one of my favorite vocalists) Also, this fixes the only complaint I had about the original: speed. The upbeat tempo really gets my blood racing for some dancing!
Only con (and I know it's been mentioned before), is that the transition at about 3:01 is a little awkward. It just cuts off without any warning. (Not good for dance, it needs to have a flow) My advice: try fading the two parts together so the previous part bleeds into the new melody. Other that, fantastic!