GarageBand '11 is the latest iteration of Apple's recording studio application. With it you can record instrument and vocal feeds (with the right interfaces) or audio tracks, then mix your magnum opus. There's a built-in "learn to play" feature for both guitar and piano. GarageBand '11 installs easily but is a large download, and costs $14.99.
The GarageBand '11 interface is split into panes. The main area shows you tracks layered one on top of the other. Beneath that is an output track representation. To the right are images of devices and effects you can switch in and out. The bottom of the window shows some common playback controls. A number of expanding menus let you access less-often-used features. The interface works well and won't take long for anyone to learn. New to this release are some additional lessons (which are good examples of playing in different styles) as well as a "how did I play" feature that assesses your performance. There's other tweaks with GarageBand '11 over early versions, all worthwhile.
We had a lot of fun with GarageBand '11. From playing guitar and keyboard through a 24-bit audio interface and applying various effects on playback, through to playing around with sound envelope parameters, there's a lot here for very little money. Compared with much more expensive applications, GarageBand '11 has a lot going for it, and unless you're in the advanced user category, this will be more than enough for you.