I have this same stuck at loading screen issue.
I used the recently updated crosstie for installation. I managed to get this far without disabling PEG or using legacy X. With disabling PEG and using legacy X, I get the same results. If I only disable PEG and don't use legacy X, the client crashes due to an "unexpected error." I tried each of these configurations several times (after closing and reopening the application using the correct launcher).
One things I find weird is that as soon as the loading screen opens, there is a little spinning circle/arrow thing at the bottom right. It spins for a few seconds, and then the "Loading..." text shows up at the bottom. Right after the circle/arrow thing finishes and before the "Loading..." text appears, the game changes resolution slightly. I'm not even completely sure if it's a resolution change or just a weird shift, but it seemed to be something worth noting. This was also the point where the client crashes, right after the circle/arrow thing finishes (when I disabled PEG only).
I was going to do more tests with console open and such, but the client is telling me that there is server maintenance, so I will wait until later.
(Using: OS X 10.8.4, quad i7, GT 650M, 8G DDR3)