Have you ever watched a movie in an IMAX theatre? Personally I think it's better to watch in 2D than 3D if you have a choice. I've been going since the early 1990s. They are spectacular! A bargain if you consider the millions it cost to make one. Beware of the liemaxes though. They don't have the 4 or 5 story screen or the 10,000+ watt sound system of a genuine IMAX. I strongly recommend everyone go to at least 1. Put it on your bucket list. : )
Real IMAX theaters (mostly at large museums) are absolutely worth it, but like you said, the LieMax theaters are a total rip-off. It's taking since time for people to realize it, but in the long run that will turn out to be a huge branding blunder.
When I lived in Michigan, I saw a lot of movies at the Henry Ford Museum IMAX (which I understand is no longer an IMAX screen). Even up-converted movies were great, but natively-filmed movies like The Dark Knight were absolutely stunning. With the membership discount, movies were actually cheaper than going to a theater chain.
I've tried it. I've got astigmatism so it kind of messes with me. I don't think its something I want to keep doing. 3D movies seem overrated to me as well, and not worth the extra price. I suspect its a "guy thing" and am interested to see how many women really love IMAX/3D and prefer them to regular movies.