Having uses screen protectors for a while, they are worth it. Tempered glass is great against scratches, not so great against impact.
I'd rather crack a glass screen protector than a phone display. Now thats out of the way....
Right now you have 2 choices of screen protectors. Plastic film ones, some of the newer ones provide 100% coverage (like SGP 3D Film), but never feel as nice as glass and will get scratched eventually.
Glass ones feel like the phone phone screen, and if properly applied appear almost invisible. Right now though they don't cover 100% of the screen. This will be resolved over the next couple of months. The Samsung S4 had a curved screen and the initial glass screen protectors didn't offer full coverage, that changed later.
It takes time to make a product, and even simple things like screen protectors would have started production before the iPhone 6 was officially announced. Now they are out, expect to see better quality ones appear soon.