I suggest sorting through the last few pages of posts from jarmor - he had the same question about going on a Wednesday. Lots of good info there.
It's peak season - so even a Tuesday this time of year will see a good size crowd. Though it's not been as crazy as last summer when GateKeeper opened.
It would also helpful to know some more info - like if you're staying on-site, how many in your party, what your goals are ride-wise - like certain flat rides you want to do - coasters (if any) you are ok with skipping etc. Have you been to the park before, etc.
Weather and mechanical issues can also have a big affect on how productive your day is.
Regardless - you'll be at the best amusement park in the world - so just make sure to have fun - and based off your location - you'll have plenty of chances to get to know the park in the future.
I'm going with 2 other people and not staying on site( I'll probably get there before noon but not at opening). Flat's wise I'm hoping to get on Power Tower, MaxAir, and if its somehow open, Sky Hawk ( Compared to other Screamin swings it's definitely been slowed down. Less swings to the top and It isn't even thrusted downward any more) I'm Okay with skipping Mean Streak, Mantis, Mineride, Iron Dragon, and possibly Wicked Twisted and corkscrew.