Since the achievement list on the site (as of posting) is still using the old graphics, achievement titles, and descriptions for the original 12 achievements, here's what the changes are to the actual achievement list are:
Ranked Player: Reach Rank D in Ranking Match (online)
Magical Challenger: Complete All Challenge (Challenge mode)
Case Closed: Complete Story Mode with a ghostlop character
Marathon Begin/Half/End: Complete 25/50/100 levels in Marathon Mode (respectively)
Are you Ready: Create a lobby and invite a friend (online)
Average chainer: make a 15 chain (story/versus/marathon modes)
Long Chainer: make a 20 chain (story/versus/marathon modes)
Extrem Chainer: make a 25 chain (Team Versus(?)/marathon mode)
2 secret achievments (Flat Detective and Mushi Mushi, obtained by unlocking McCoy and Mushman, respectively)
Magical Combo: Renamed to Short Chainer, requirements still the same (make a 10 chain).
Ghost Lop: Renamed to Magical Victory, requirement changed to "win a match in under 60 seconds". Currently, Giant Bomb lists the old requirement of "unlock Ghost Lop mode"