Ive contributed to two so far.
First one:  Shael Riley and the Double Ice Backfire.  Help us get our new album properly mastered.  Or something like that.  I paid 35 bucks.  I was supposed to get posters, art books, cds, etc... lots of stuff.  Two years later, nothing.  Then i update my address in the system after an email, 6 months go by and nothing.  I contact Kickstarter, and they say im essentially out of luck.  So i finally have a back and forth between Shael, he blames his live drummer, and I end up getting a refund.  There seems to be almost nothing one can do if they get screwed over, so even though you like a band, be careful.
Second one:  Wasnt kickstarter (cant remember the name).  Ringo Deathstarr needed money to record album in a proper studio.  I sent money, am supposed to get digital album and t shirt.  My fingers are crossed that they dont leave a bad taste in my mouth, because I am about done with the kickstarter style funding.  I would much rather buy a shirt at a show or a poster at a bands webstore, to help them out, than to just pledge money that I might get rewards for.