Personally I'm just using the Black Bumper, and I'm a field service tech that gets into a lot of nasty environments, mostly can scratch or break the glass. I've had my 4 since a week after launch, preordered, and don't have a single scratch on either the front or rear, and I'm not being super careful, just doing my normal routines. I am using a Marware drop in hip case, no latches, that I got for the 3GS.
Now, as far as screen protector companies... I don't like Zagg one bloody bit, I got the cover for my iPad Wifi+3G, let it cure just like they said, and two weeks later the screen protector is covered in tiny scratches from my finger nails (not long, just at the tips of my fingers) and is so dull I can't see the screen clearly. After three weeks and trying to clean the cover I got so fed up I ripped it off and threw it out. I use the Apple iPad cover and no screen protector, take it to work and haven't gotten a scratch or nick. Plus my two year old daughter watches some movies on it and use the preschool apps I added, yes I know she's an exception to the rule of toddelers who are more likely to throw an iPod or iPad, but no problems.
Ipersonally can't make a suggestion for anti scratching, except invest in the Apple branded products. If you're concerned with finger prints, iKlear is the best cleaning kit I've seen so far. Works great for me. Hope that helps.