I've hunted OTC units 16 and 42, I believe. I've almost always hunted the last two weeks of season, more to get away from other hunters than anything else.
Lots of folks go early, the first two weeks, and I believe ML season is the third week of the season, maybe the second. I've found the last week of season to be much more serene.
As Pistol Pete notes, the elk have been hunted hard and are more spooky and often holed up in some pretty isolated cover. But if you find them, can have a very good hunt.
Probably see more elk early though because there are so many folks chasing them around.