in what way do you feel limited?
With the 7D I felt limited with the final image quality especially having to take most of the pictures late afternoon and continuing until night with no natural light.
Having seen the 7D prints and 5d mk iii prints, the 7D sure falls behind. Not that it's not usable, but I would like to deliver a better final product for the client.
Don't get me wrong, I love my 7D, it's fast burst and that extra reach is amazing but all I want to see is the FF capabilities and advantages over the crop sensor.
In the meantime, I don't think I'll be able to sell my EF-S glasses or the 7D due to my current location BUT I would still like to keep my 7D as my backup camera.
As for the 600RT, it depends on what your goal is. If you know you will be using wireless off camera flash, then it may make sense to get the radio flash. I don't have any experience with it though, as I used my 580 EX IIs and 2 430EX IIs with pocketwizard flex TT5s, and that's a fairly expensive and sometime finicky setup. So it really just depends on how you want to use your flash.
(PS. Wireless off camera flash is the way to go. Just sayin'. Once you start seeing how great your lighting can look with modifiers and the freedom to move your flash wherever you want without tripping over cords, you will soon have a case of lighting equipment upgraditis as well)
Thanks for your feedback, I guess I'll have to do more experimenting with flash and then see how it goes.