The folks at Shield Zone sent me half a dozen iPhone and Palm Treo Invisible Shield screen protectors to try out.

While Apple’s iPhone has hardened glass that seems impervious to scratches (as demonstrated by CNET and a few other sites), the super-smooth screen is a total smudge-magnet.

Hours after owning the iPhone I began to perfect the left-pec-screen-wipe maneuver to swipe my screen clean on my tee-shirt every so often. So though the Invisible Shield is meant to protect your screen from scratches with its ultra-strong plastic material, I’m more grateful for the way it minimizes the smudge factor with its watery finish that offers a bit more tactile touch-feedback under the fingertip.

I blew it on the first two I applied – mostly because I was hyper-aware of not touching the sticky side of the sheet because I was afraid a fingerprint would appear. Following the directions, I sprayed both sides of the sheet (and my fingertips) with the supplied fluid and set it onto the screen, sliding it this way and that to align with the speaker hole and the home button at the bottom of the iPhone. Because I feared time was of the essence I tended to do my best to move it in place, then, using the supplied squeegee, squeeged out bubbles. Both times I found dust beneath the surface of the Invisible Shield.

Trying a third time I was super-careful to make sure there were no dust particles on the screen, sprayed my fingertips and the shield, then applied it and took a little more time to get the fit exactly right. This time I nailed it – but at $14.95 a pop, take my advice, don’t worry so much about being gentle, and concentrate more on making sure you have no dust on your screen, or your fingers, and then take a deep breath and relax as you move the slightly slippery screen this way and that to get the fit just right.

Once you do, squeegee away the fluid, and if possible, keep your hands off the iPhone for the recommended 24 hours. That wasn’t possible for me, and in my case it didn’t matter – as the Invisible Shield “dried” it seemed to tighten up nicely and I’m absolutely pleased with the fit and finish.

Sheild Zone offers a costlier version that provides the same plastic protection for the backside of the iPhone, however I skipped that, as I’m only concerned about the screen staying scratch-free and, the real win for me, lessening its smudge showoff factor.

As an aside, I also applied the Invisible Shield for Palm’s to a Treo 680 and it turned out great, though I have to say the feel of using a stylus against the shield’s slightly tacky surface feels a bit stuttery rather than smooth.

The iPhone shield texture feels the same, but under the fingertip it feels like there’s less drag/stutter.

Bottom line: The Invisible Shield for iPhone (and Treo and other devices) offers great protection while hiding smudges.