The really big deal about rooting in the beginning was that there was not a way to fix it if it b0rked. Now, except for one step, everything that b0rks can be fixed (and, ironically, IIRC, that step is actually in the first step to fix a b0rked phone...)
Technically, rooting does violate your warranty, but as numerous people have said
ad nauseum, you can always take your phone back to stock if you need warranty work performed...
Of course, if you have 5 or 6 apps that require root, and you leave those on there, then it won' take a rocket scientist to figure out that you had a rooted phone at one point or another....but that is easily fixed by removing those apps. Preferably
before you 'un-root'.
If you are even considering rooting, I
highly suggest that you take a look at
http://androidforums.com/all-things-root-droid/82742-all-new-guide-all-things-root-related.html and read it all carefully - especially the sections in red and yellow. No matter how much of a techie you are, trust me - reading and understanding and comprehending this info and asking questions will save you a lot of headaches.
I rooted sometime in Jan, I think, after see-sawing for a long time. I didn't have a single glitch, except for user error, and I figured that out pretty quickly and on my own (I think...lol - been so long now). and I have been working with computer hardware for 22+ years, and am considered the go-to guy for most questions 'tech' related in my job and at home.