Hi there! Great questions!
1) The suspension IS completely reliable. Obviously because you're using someone's $200 smart phone you would want something to be safe :) The gimmick does all the work and you can feel comfortable in knowing it will hold!
2) Just about every smart phone you find will work (iPhone including!). If you're performing in a group of two or three people its almost guaranteed you will find one that works, and they're easy to spot.
3) The trick DOES work with a case on, but some may not. I haven't tried all cases yet but I believe some of the otter boxes and life proof cases may get in the way.