I'd hate to see it turn real-time - that's what Age of Empires is for. I wouldn't mind the damn things taking a bit less time, sure, but I still want them to exist!
There's a few features relating to them that I'd like to see - for instance, I've had a few cases where I've "spaced" a unit to skip its turn, then later found I'd wished I'd used it, but when I click on it, it's already "moved" - now that's not logical. I should be able to un-skip it ... But really, Civ is a game of turns, and should stay that way.
(No problem with it being an option for those who want it, of course!)