Good interface; playlist management and BPM slider needs some work.

PROS: Definitely better than some of the other tempo apps out there. Interface is simple enough to use and the big slider makes things easy when jogging or working out. The slider allows for a nice range of tempo change. The tempo percentage slider works perfectly.

CONS: A little pricey for an app, and Im not convinced its worth it. BPM tempo change is a little buggy - like any BPM detector, there will be some songs where it cant pick up a beat, but there are times where it seems to be constantly adjusting and cant pick up obvious beats.
Song list cant be shuffled, so you either have to manually add things in the order youd like, or hope you like listening to playlists in the same order every time. Song list cant be edited once running - if you forget to add a song, you need to re-add the entire playlist rather than adding or removing an individual song.

IMPROVEMENTS: It would be great if this app could read manually entered BPM info in the MP3s tags, rather than having to autodetect all the time, especially with some of the slower songs the beat detection doesnt work with.
The playlist management needs some work: the ability to shuffle at the very least, and the ability to modify a playlist (i.e. add an additional song/remove a song) rather than having to start from the beginning each time would be nice.

BOTTOM LINE: if youre looking for something that will change tempo by a certain %, maybe for a dance class or DJing, this app works well and is likely worth the little extra cost. If youre looking for something that will maintain a constant beat across songs for cycling or jogging or something, BPM detection is spotty and this app doesnt maintain a constant beat terribly well. The big slider interface could be really good for on-the-go adjustment, but the poor playlist management really inhibits it - you really need to plan your playlist ahead of time.

Taylor B; Toronto, ON about Tempo Magic, v3.1.3