According to McCarron, the new DVR appears to be a “revised Series 3/HD model aimed to lower production costs”. He explains that:
The main differences I can see is that It features only one Cablecard slot, which is said to be for Multi-Stream Cards only. It no longer has the S-video output and phone jack. It also seems a bit shorter than than the TiVo HD is, judging by the spacing of the component video jacks. The second page also shows the TiVo software’s CableCard UI with just the single slot on the screen, which is clear this is for a device with just one CableCard slot.