Went to Apple store last Friday and got my iPhone 5 replaced with a refurbished one which looks brand new.
Although there were reports about some iPhone 5 not been fixed/replaced by Apple, mine was replaced without problem. I guess it might be because (1) mine was also eligible for the sleep/wake button replacement, (2) I experienced an instant battery drop from about 80% to 0 around 2 weeks ago.
The service was quite good and only took about 30min, much shorter than expected. I was really worried about the data, and did 2 backups before visiting Apple store.
Surprisingly everything back to normal quite smoothly after data restored from iTune. Only issue I had was as below. Because iTune tried to restore all the games/apps I purchased before, there were 195 apps to be installed and iTunes shows it's "Over Capacity by 147.6 MB"!! I have to manually delete quite a few old games/apps during the restore.
A slight correction, I later found that all previous PDF and other documents I manually added to iBook through email or dropbox disappeared, plus all test apps I installed from XCode also disappeared.
Don't understand why iTune doesn't backup these 2 areas..... That is something you have to be aware of before restoring from iTune.