The catch is that the 360 box is not as good as the V6 and is missing a large number of features. The change is because Liberty Global own the 360 software and use it on their boxes in other territories, whereas the V6 software is licensed from TiVo, eventually everyone will be moved over anyway, but I certainly wouldn't do anything to speed up that process!
Some of the missing features are as follows; Wishlists (where you can set the box to record programs on certain subjects or featuring certain people), undelete, series link+, series link manager, suggestions, setting of series links for programs not in the current TV guide, ethernet control, keyboard support via USB, switching between tuners with constant buffering, skip-back on fast-forward, quickplay, default recording options, cancelling individual recordings from a series link, multi-channel series links, radio channels allowing recording of radio, separation of recordings between boxes, watching recordings when internet is not available and probably a few others I've forgotten.
Also, extra boxes do not have their own hard disks or tuners (unless converted from a V6 box), so you lose storage space and recording ability and are also reliant on the main box being on to watch and set recordings and also on having a decent wi-fi signal (or ethernet cable) between the two boxes when watching recordings.
