Nice set! despite being challenging to use, ain't the MP-E a fun lens? I have no regrets buying that one, but I should use it more often.
It is fun! There is so much to see that I haven't seen before. Studio shots are easy (tripod + focusing rail), but the true nature shots are still very hard for me. I'm improving, and I know there's light at the end of the tunnel. I'm 65, and my hands aren't as steady as they used to be. Using a good monopod for the nature shots is helping quite a bit.