I've gotten invisibleshield and best skins ever. Honestly, for my money's worth.. I plan on just getting bse from now on. I can't tell a difference and if I needed to replace the bse, it's still cheaper buying a replacement than relying on invisibleshield's warranty. difference? packaging. bse comes in a plain envelope, no spray bottle of "solution" (soapy water) and no little thing to work out the bubbles (use a credit card)
there's "bodyguardz" as well which is sorta a halfway point between invisibleshield and bse. price point is about the same as invisibleshield but it comes with two skins and better packaging.
checkup on ilounge's reviews. they have a review on each one for the iphone.
http://www.ilounge.com/index.php/ipod/review/11445/