I recently bought a Retina MBP, and it's the first computer I've had with an SSD. The difference in just about everything was pretty surprising. I remember trying a reboot in the Apple store when I was debating getting it, and it took around 12-13 seconds. My 2010 MBP at the time was taking I think well over a minute to boot since I got Mtn Lion.
But more than that, it's great in music apps. My Omnisphere presets load almost instantly as fast as I can select a new sound, all while recording and playing back 96k audio. HD meter doesn't even move in....errr.... some other DAW.
Im considering buying the 512gb ssd or a 1tb 7200rpm hd for my macbook pro, i've seen alot of mixed reviews on SSD and music production software so Ive been holding out