I'm having the same problem, the spacebar is just not as responsive leaving most of my texts in one large word w/ no spaces. It's very irritating. I've had the phone for a week. If you google the problem many people having the same issue w/ the iphone 5's. Apple really needs to address this problem. I'm not gonna debate if it's hardware or software, it just need to be fixed. For as much money as we pay for this phone and the size and reputation of Apple, they need to step up and get this resolved.
Unless and until basic troubleshooting is performed, there is nothing for Apple to "fix".
Considering this the only thread I have personally seen, and I'm here daily, I'd say it's a non-issue.
If it were wide-spread, there would be media outlets blowing it completely out of perportion just like "antennagate".