I used a skin from bestskinsever on one of my BB Curves. It lasted quite well and really protected it - just like the ones form ZAGG, but at a much cheaper price. They use essentially the same material, but they send it to you in a plain envelope rather than a custom created box with all sorts of graphics and a bottle of application liquid. Instead you download instructions from the bestskinsever web site which tell you how to make your own liquid from dish soap and water.
When I tried a ZAGG shield I found that the bottle of liquid didn't work all that well and there wasn't nearly enough anyway. For the money, I'd get a bestskinsever skin over a ZAGG, make my own liquid and use a credit card to apply it. Also, the one time I ordered from ZAGG they sent me the wrong skin and then required me to send back the wrong skin in order to get the right one - not a great CS experience given how much profit margin they have on these, they could have just sent the right product to keep a customer happy but they didn't feel the need...