I truly, truly hate heirlooms.
I'm working on a toon that's BiS will only require one (So far, that I can tell from data) on f2p, mostly because of this. Another thing is, that I've mostly been twinking at 60,80,85 and such due to heirlooms.
I just feel they take out so much of the fun of gathering the items, farming, grinding. That's half the reason I twink, because it's more similar to how MMOrpgs used to be. Granted, there are always pieces you can pick up on the AH at high prices, but I'd prefer that even over heirlooms.
Having every single piece, or close to it being all heirlooms just feels so cheap and homogenized.