I LOVE hipstamatic! Use it all the time as you can post pics straight to FB and they always look good better than my usual rubbish
My Dad is a photographer and he loves it so much he has brought all the extra packs. One of his friends (another photographer) has an amazing website of pics she has taken with it. Can't remember off the top of my head what it's called but will ask him!
I have brought two add on packs but draw the line at spending more + it's already really good (and I can't get my head around all the combinations as it is!)