It depends on whether you're in a Motorola or a SA/Cisco system/area.
The Xfinity X1 (»[X1] Xfinity TV on X1 Platform and X1 Remote Control App!) is the latest, but has limited availability right now.
For Motorola systems, the latest DVR models are the DCX3400 and DCX3501 (aka the Motorola RNG200N): »Motorola DCX-3400 vs. DCX-3501?
For SA/Cisco systems, the latest DVR models are the Cisco RNG200 and RNG200N (AnyRoom).
You can see these models and get a copy of their user manuals here: »customer.comcast.com/help-and-su···manuals/
There was also this recent thread: »[DVR] Latest Comcast DVR