One of my favorite apps is now compatible with the iOS4. I haven't used SnapTap because I've been waiting for Snappy to be updated so I can't compare. However, with this tweak, you can use the volume buttons to snap photos and can launch the camera from any screen using Activator (lockscreeen, in the middle of other apps without closing them) and start taking photos in 1 second! Definitely a useful tweak and well worth the $1.99. 