Posting this from my six month old Macbook Pro 15" on which the spacebar has just started doing double spaces. Going to try and clean it with compressed air, but even if that works, it's unacceptable in my opinion that such a key piece of hardware on such an expensive machine should be so fragile. The fact that at some point I'll have to take it back to Apple and probably be without it for several days due to the com…
It's unlikely to take days. A few months ago they replaced a broken key cap for me in about 20 minutes.
https://www.youtube.com/watch?v=4KuVvb9DTaU (from about 5:20) talks a bit about what's involved in an actual keyboard replacement, if you ignore some of the histrionics.
I think from what I've heard that for actual replacements, Apple will swap out the whole 'top case' subassembly, which could be a 4-500$ part if it's not covered under warranty.