This has happened to me on 6.0 and 6.0.1 now. Only fix I've found is to restart the phone. Basically, at some point anywhere from hours to days after a reboot, the typing tap tap sounds will start lagging and stuttering when I'm typing. Anyone else experiencing this? If not, I'll try a full restore but would like to avoid that if I can. Have already done a restore with backup and that didn't fix it.