I started off with the one sold through VZW, but was never 100% happy with the way those seem to never fully align (work at VZW, so have installed scores of protectors on a wide variety of devices) with the screen particularly up in the upper right near the proximity(?) sensor...I had a customer come in a while back with a Storm that had the Zagg Invisible Shield and was I impressed by how it looked, so when I happened to be in Best Buy the other day, I decided to give it a try...
I paid the extra $8 to have the representative install it, and I think she did a pretty good job...
I can relate what a few have mentioned above in regards to the 'orange peel' thing, but on mine it is really not pronounced at all, however I can imagine if someone was to install one and didn't have any experience in doing so, it could possibly look kind of ratty (for lack of a better word).
There is definitely a 'sticky' feel to it compared to the naked screen or the other protector I had on it, but I have noticed that as the days since its being installed have passed, it has felt smoother and smoother.
What was interesting to me was that the rep who installed it told me that it was going to look a little weird for the first few hours, some bubbles may appear but would go away, be careful with it for a while however it would look great within a couple of hours, and she was right... also, as someone mentioned above, it tends to ' finger oil' smear less than with the previous protector installed or when 'naked'.
Just my .02