In fact, it's the second best running edition, after the PC one that is. From someone who's working on the game, posted on the SEGA Forums:
I had doubts of buying this edition of the game in the future because of that issue, but it is nice to hear that it has been solved.
Source: Sonic Stadium
For those of you who havent listened to Sonic Talk, Lycetts explanation for the poor performance of the Wii U version was the simple fact that the demo the critics were playing at GDC was based on old code. Since then, more previews have come out complaining about the frame rate issues, but thats probably because its the same exact demo. SEGA will typically use the same demo across multiple events, as it takes time to make a new one, and according to Lycett on Sonic Talk that was time the team simply did not have.
I had doubts of buying this edition of the game in the future because of that issue, but it is nice to hear that it has been solved.
Source: Sonic Stadium