I ALWAYS ALWAYS get screen protectors. Despite the fact that people say that the screen wont scratch. I dont like the thought of change or keys touching my bare screen, regardless.
Plus, if you notice, after a while with a screen protector on, the oils and such from your skin create a residue that is stubborn to come off... I just changed my screen protector that was 9 months old, and it was amazing how much residue was built up.
And EVERYDAY, I take a microfiber towel and wipe my phone down.
It's really up to you, however. I say, why not be safe?
And in my opinion, I don't think my protector ruins the feel/touch or look of the retina screen. It's a crystal clear protector, so the colors are just as vivid.
My next protector is going to be matte. I like how the matte protectors seem to hide fingerprints.
And if you do decide to get protectors, don't feel the need to spend a lot of money. I've had good experiences from cheapo ones on eBay. It's all about how well you can apply them. As long as the edges line up well, it wont peel and dirt wont get stuck underneath.