This came up on a thread about M&Ps on Smith-WessonForum.com (HERE). It reminded me of a conversation I had on Friday with a coworker who carries his Keltec P380 unchambered. I wrote this response and thought I would post it here...

The problems with carrying empty chamber to me are:
1. Requires the use of two hands. I don't know about you but I am usually carrying stuff. Yes, I will drop what I am carrying but those extra seconds could cost..
2. Relies on more precise motor skills than I prefer to have to use under stress. Consider that you may have to do this moving, or taking cover
3. Requires that everything during the charging sequence to work and charge the pistol. If any one thing fails then the pistol is essentially a big rock. For example, what if the bullet fails to chamber, or the slide doesn't completely go into battery? You have essentially a rock in your hands.

This is exacerbated with one handed racking. Not only does your equipment need to support this (flat pistol sights, hard belt or hard holster), but you will need to clear your cover garment and rack the pistol, with the same caveats as (2) and (3) above,  without being able to see what you are doing (do you really want to look away from the assailant?) and you may possibly be in motion.

Definitely not something I want to have to rely on, especially during stress and with an assailant. So, I guess to answer the OP's question, yes I carry chambered. :)