IKs newest app, DJ rig, is designed for use with their newest product, the iRig MIX. However, this app has potential to be used apart from its companion hardware. For $7 (including the in-app purchase for the "pro bundle") you get 12 FX, a 3 band EQ (which doesnt completely kill sound when set to minimums D:) two decks 4 cue points and an advanced sync function that is (in theory) able to line up your beats perfectly. Some features, such as the X Sync function, I havent tested because I dont have the requisite hardware (an iRig mix) but I will update this review once Ive tried it.
Some cons: the sync button very rarely gets my beats lined up (I mostly play dubstep, which has some tricky beats, so Im not too surprised. It works very well with 4/4 electronic music though)
Also, the search function is very slow (and I do mean VERY slow) on an iPad 1
Lastly theres no iPad version, but as I understand that will be corrected for future versions