I got tickets for this monday in chantilly at the air and space center. Although, they're probably all sold out for the first week by now.
Now onto your 2nd question, is it worth it? When I saw Superman there, the opening credits ALONE were worth it. It's such a different world in imax. You truly feel like your there. And, only costing 2 dollars more than a regualar theater, it's most definately worth it.