Never having used one, I wasn't certain whether I would like a red dot or not, so I bought a cheapo Simmons for my 6-7/8 Mark II. I figured if I didn't like it, I could sell it for a few bucks and not be out too much. That was almost 10 years ago, and that same cheap red dot is still on the pistol.
Granted, it has a soft life - it's only used for target competition - but it works all the time and holds zero. Unless you anticipate needing something really rugged, don't overlook the cheap ones.