I have a DCX3400 from Comcast. I also have both the silver and gray remotes.
I was told the gray remote is needed with the DCX3400, but the old silver one seems to work fine. The silver one can still add the 30 second skip and the gray one can't so guess which one I use?
The DCX3400 might not be perfect, but if I went with Tivo or Moxi I have to pay for the box plus monthly fee. The Comcast DVR is $16 a month, but I don't have to pay the $7 HD fee.