When you do scratch your screen you will wish you had used a screen protector.

I've been using a Vikuiti™ screen protector DQC160 on my n900 for over a year now and the screenprotector has some minor scratches and one small deeper scratch.

I will be trying the Martin Fields one next...

BTW, there have been numerous interesting threads before about screen protectors so if you want to read about them, just search