Looks good on paper, in practice not that helpful IMO. THe coach ride when traffic is decent is only 30-something minutes anyway, and that itself has never been the biggest issue for me. It's collecting your bags, lugging them across to a coach/train station, getting on and off the transport, paying for it, re-clearing main security lines etc etc. I have to say when BA used to comp the trip and move your bags for you (pre-9/11) I found the connection straightforward and doable in 2 and a bit hours, not much more than you would have allowed for a LHR-to-LHR connection with transfer from T4 to T1. Buses do seem busy, though, so I guess there is a significant pool of users for the service.