I installed one of the compatible door locks myself and it was fairly simple... took me about a half hour or so and pairing was simple.
There is only one model (with three different styles: bronze, sliver, and gold) that fully integrate into XFINITY Home... meaning you can control it via the Touchscreen, X1 App, online at home.xfinity.com and via the Mobile Apps... and that model is the Zigbee version of the Kwikset Smartcode 914.
Pretty much the only place you can find it is online through Best Buy here: http://www.bestbuy.com/site/promo/xfinity-and-kwikset-134972. The Smartcode 914 is sold in stores and on eBay, but that's usually the Z-Wave version that is not compatible with XFINITY Home... you need the Zigbee model.
I've been very happy with the lock. I like that you can program multiple codes into the keypad and that I didn't have to change keys from my previous lock (you can set it up to work with any key).
The other lock you can get is the August smart lock, which you can get here: http://store.xfinity.com/xfinity-home/index.php?v=comcast_xfinity-home&nvbar=XFINITY+Home. It's also available on other sites and in stores. It's part of the "Works with XFINITY Home" program. I won't comment on the quality of the lock since I don't have one... they look nice but unfortuantely they aren't fully integrated into the XFINITY Home system... you can only control them with the mobile app for now, and you can't set up Rules to control them.
Let me know if you have any questions about the Kwikset!