New phone purchase -- InvisibleShield a good choice for protection?

Hello everyone. I'm about to switch to AT&T Wireless in the next few days. Looking at all the phone choices, I'm going to get the Samsung Impression as my new phone. I really want to protect the phone from scratches. The mall that I go to has an InvisibleShield Mall Cart right outside the AT&T branch store. I was thinking of going there right after I get the new phone and purchasing their installation services.

How good is the InvisibleShield for the Samsung Impression? I ask this because I have never used this product or any skin protectors before. In fact, this is my first time purchasing a touchscreen phone, so I just want to get it protected ASAP. The convenience factor is really the main thing I'm aiming for, so the InvisibleShield seems like a viable option.

Also, I've read in the other threads that the body protector for this phone is rather troublesome (i.e., something like it covers the moisture sensoring point, thus voiding warranty, or just that it is really hard to put on). Should I just get the screen protector alone instead?

Thanks!