There are many multi-track recording apps in the AppStore.
However, this app is special because of its distinguishing features described as below.
ezRecorder supports 7 multi-track recording and various effectors like reverb, compressor, distortion, etc. It also supports action recorder which enables record your behavior during recording. So you can record volume, pan controlling and real-time effector controlling. It includes 177 HQ drum loops with various tempo.

appstore link :
http://itunes.apple.com/app/ezrecorder/id516476326?mt=8