I kind of like the fact My Colt is pretty rugged looking but I wasn't sure if Reblueing did anything else other than cover up the wear and tear? Does it do anything else besides make it look New?
Blue is controlled surface oxidation. It is very little rust protection, no wear protection. Purely cosmetic. A poor reblue by somebody who doesn't know or care how can do more damage than it covers up. Overbuffing, afterrust, and bluing salts creeping out of crevices are too common. I like my guns showing the use I have given them. Character and all that.
I agree that rebluing will usually reduce the value of a collector's gun, but a good re-blue job may make a shooting or hunting gun more saleable. Of course, a poor job, with rounded corners, buffed down markings, and slotless screws will do far more harm than letting the gun alone.
As to protection, bluing is controlled rust, and it will hold some oil and prevent further rust better than plain steel.
I guess it depends on who does the rebluing! I've owned many blued guns and NEVER had a bit of rust. I don't "baby" my guns, just wipe them off with a clean cloth occasionally. Different people may have a different chemical composition in their sweat, though, and blued guns don't work for them.