What is it you've read about "incomplete program guide"?
360 is substantially different to TiVo/V6.
I read that it only has info about programs that will actually be broadcast soon, whereas Tivo has program info for all shows. So for example, if my favourite show is not being broadcast for a while I could not create a series link ready for when it is broadcast next (like I can on Tivo). Not sure if that is true but would welcome clarification on this as I've got a list of series-link items I would want to transfer (manually enter - I guess) if I ever do upgrade.
I have a V6, and after asking questions about this both on here and talking to a Virgin tech' I know, I would stick with what you have. It certainly doesn't look like the 360 is in any way an 'upgrade' as we would think of it.