I use Peel & Seal in many repair applications, some fairly large areas. I've done a few small low-pitch roofs with it too.
Their website is really poor:
http://www.mfmbp.com/ccp51/cgi-bin/cp-app.cgi?usr=51G483613&rnd=6791991&rrc=N&affl=&cip=&act=&aff=&pg=prod&ref=PSalum&cat=RMs&catstr=HOME:RMs
Their installation instruction and data sheet tell you a little more:
http://www.mfmbp.com/install.htm
http://www.mfmbp.com/spec.htm
Using it -- as is the case with many peel and stick products -- isn't quite as simple as peeling off the backing and slapping it down. To get good results requires proper surface preparation and careful installation techniques.
I'm trying to remember the oldest jobs that I've used it on -- I'm thinking some of my uses of it go back about 10 years. It is still holding up very well in those locations.
The only problem I recall with it involved the "white" finished material; the white top layer peeled off after a few years at one location (fortunately it wasn't visible). I suspect it was a problem specific to that particular roll/lot. I stick to using the plain aluminum in most applications since a colored face usually isn't needed.