I know alot of folks who hunt right alongside the muzzle loaders. In my unit, however, I tend to avoid them - there are just too many, and they tend to be the 'ride around on an ATV' crowd - not saying there aren't bowhunters who do the same, but they are fewer.
Alot depends on how you want to hunt. If you're primary interest is calling & hearing elk - I would go Muzzleloader or the last week of the season - granted the elk may be reluctant to actually come in because they'll be herded up, but at least you'll hear them.
Early on is a good time to use passive hunting methods - tree stands, ground blinds, or quiet spot & stalk. If you go early, I would suggest going a couple days before the opener with the hopes of having some elk patterned for the opener - I think this is one of the best times to get one as you can hunt undisturbed animals. Also, if you want to shoot any elk - this IMO is the best time, since they are in smaller groups, and a little more disbursed, you have a little better likelyhood of bumping into one within range.