Yes, IMO. I can imagine this list has a preponderance of people that would miss the binding, though. Personally, even though I have always written more elisp than the people immediately around me, I'm a C/C++ programmer, and mark-sexp doesn't do anything intuitively useful for me in c++-mode, so I've never internalized it.
Even though I voted for C-x SPC, I would miss gud-break. Lots of muscle memory around that, although not as much as Alt-Space. I suppose the M-[ and M-] suggstions aren't so bad.
Oooh. s-SPC is free. I shall bind it to s-SPC in my own .emacs anyhow.