I am posting this because a lot of people have posted about how hard it is to install a Zagg InvisibleShield on the iPhone 3G. I just put mine on and found it to be relatively easy, so I thought I would share a few tips in case it benefits anyone else.
1) Some folks complain that for best results you have to leave the phone off so it can "set up" for 12 to 24 hours to let the product cure. I simply installed mine at night so it can do most of its setting up while I am asleep.
2) Use the shield spray liberally! I ended up using the entire bottle just putting on the back piece because I had to realign it once and I wanted to keep my fingers moist. You can refill the bottle up to three times, so do not worry if you use a lot.
3) The corner pieces, were indeed, somewhat hard to do. They sort of stuck where they fell when I first placed the piece on the phone, so I had to peel them up, respray, and then press down again. Letting them set up a bit definitely helps as does the "palming method".
4) THE BEST ADVICE I found online was to stretch a piece of saran wrap over the top and bottom of the phone to help keep the corner pieces down while it cures. I did this for about 10 - 15 minutes only as I did not want to trap any moisture from the spray, but it did make a difference. My corners are all now nice and smooth.
The squeegee really did get most of the bubbles out, but some very small ones will remain. Zagg says these will work themselves out as the products settles down over the next day or two. I have been checking periodically as I let the phone sit, and indeed some of the small guys are already gone.
So far so good. I really like the shield and the phone looks great. I will still use my case for drop protection, but now I can rest assured about scratches.
I originally had an iFrogz Luxe case that I LOVED, until I realized it trapped stuff between the case and the phone, so the chrome and the back of the phone got scratched up a bit. I was always careful with the phone too, keeping it in a sunglasses pouch when in my purse, or keeping it in a separate pocket when in my book bag, so the scratches really annoyed me. Also, one of the tabs broke off after only a couple weeks, so I was worried about the case staying together if I were to drop the phone.
I now have a SwitchEasy Rebel. The case is not as nice looking or feeling as the iFrogz (in my opinion), but the protection seems to be way better and I am not worried about pieces snapping off.
Here are some pics of the phone about an hour and a half after putting on the Zagg:
UPDATE: Just FYI, by the next day, all micro-bubbles were gone, all the corners were smooth, and it looked awesome!