Most of the time I just ssh to a remote server or keep a window with persistent mosh connection. All my stuff on the server is only tmux attach -d away!
I suppose I could compile small to mid sized programs on the Macbook itself. Benchmarks indicate it has enough power for that. Compiling something like boost or linux kernel might take a while but I don't do that very often.
In the end, I don't know. I'm keen to give it a go. I switched to 13" rMBP from Air for the retina screen and I still remember how clunky it felt.
Probably not enough to be my only laptop but wouldn't mind swapping my 13" rMBP for 12" Macbook + 15" rMBP (when quad core Broadwell or Skylake comes out).