I had a Treo before my Vogue, the screen protector was a MUST.
But with my Vogue... ummmm... I never felt the need... the screen doesn't scratch that easily. I do try to use my fingers as much as I can, and avoid the stylus at all cost, and so far the screen looks like new. I am VERY careful with it, though.
I won't recommend to anybody to "go bare back", but if you like it and enjoy the ride, be resposible and don't come back crying when you start oozing pink...