Any way to tell how many hours I've played?

I can't find it anywhere.

use Raptr: http://raptr.com/

I use total gametime as a number to help quantify the value of a game purchase. It's not a flawless system but it helps. Essentially, I should get 30 minutes on the dollar. So if I spend 30 bucks on a game, that's fine but I should get at least 15 hours out of it to make it worth it.

With that in mind, there are plenty of simple tools to help track time. Business execs use them all the time to help gauge billing cycles. Just keep track of the data in excel or something. That way you become the master of what data is and isn't kept instead of steam or raptr. So if you don't want to know how much time you spent in MW3, just stop tracking that specific game.

http://freelanceswitch.com/productivity/6-cool-tools-to-track-your-time/