I think that converting mp3/wav/analog audio to midi hasn't progressed past a primitive research project with minimally acceptable results.
Here is an example....
http://www.akoff.com/music-composer.html#samples
The samples don't sound bad, but these don't represent the complex sounds in most commercial recordings.
Although for $29, if you are just wanting to get midi versions of some riffs you create, it might work well.