INRAS but you said:
Mac's CPU seems an older model than the MBP's - that could be an issue as I run a lot of CPU intensive test suites that are on the critical path for productivity.
That's not a real reason to wait for Haswell iMacs. Haswell is mostly a win for low power, absolute performance or IPC doesn't change in any real meaningful way at the high end. Also the very high end Haswell parts aren't out yet. And a high end SNB iMac will out-perform a high end Haswell MBP on CPU bound work anyway.
FWIW I do a lot of CPU bound work, and recently got a new work machine, didn't bother waiting for Haswell for this reason (and if you need a new machine, you need a new machine, regardless of what's coming).
For me I didn't go Mac as I couldn't get the performance I needed, but I have niche needs (my personal machine's a MBP).
For reference, typing this on a i7-3940XM - not likely to be bettered in performance by anything haswell for a while, and it'll be a gen or two till there's a meaningful performance bump. So yes, I'm at the eye-bleedingly expensive high end of the CPUs, but it applies lower down the range too where you care about CPU perf.
EDIT: actually read the thread and that's redundant advice now, but I'll leave it there for others Oh and the haswell macs are out now
Regarding being "spoilt" by the rMBP - you can buy 4K displays with comparable pixel density and they'll only come down in price.
Just using the laptop screen is awful for your back (certainly for me as a taller person).