The PS3, 360, Vita and 3DS versions of the game will have both Standard and Bonus/Limited Editions of the game. The Bonus/Limited edition comes with a code that allows you to download Metal Sonic and a bonus track.
The Wii U version is considered a Special Edition, which comes with Metal Sonic and the track by default, as well as some Wii U exclusive features. --- Just imagine that you see some really funny quote here.
I was paraphrasing directly off of a post made by a Sumo Digital employee who happens to be cool enough to talk directly with fans on a Sonic fan forum I frequent. The way he laid it out is the way I described it.
And technically, the Wii U isn't getting the Bonus/Limited Edition. The PS360 and ViDS are getting two different versions of the game, while the Wii U gets its own, exclusive "Special Edition" that has Metal Sonic, the OutRun Bay track, and a handful of other features besides. The Special Edition is not just another name for the Bonus/Limited Edition. --- Just imagine that you see some really funny quote here.
I just talked to someone at gamestop and he said that the only games they are taking pre-orders on are the Bonus Edition. --- 3DS FC:0301 9783 2635 Name:SSJ4 Goku Pokemon Black 2 FC:2838 7957 0751 Name:Zack