When I got off at UWE it went straight out again with the 1715 to Gloucester. Chances are there would have been no one on that service all the way to Gloucester!
I think they need to promote it more. And think they need to modify the route. Maybe extended to/from central Bristol instead. Think they might not have permission to run from Bristol bus station, and/or there could be capacity issues. So maybe the terminating point could be Broadmead Lewins Mead. Also, not sure what the point of stopping off at Gloucester Waterwells Park & Ride is?
An example segment of a timetable could be
BRISTOL, Broadmead(Lewins Mead) 0900
UWE, North Bristol 0915
SGS Filton College 0928
Cribbs Causeway, The Mall 0935
Aztec West, Aztec Hotel 0942
GLOUCESTER, Bus Station 1022
Yes, it takes about 20-30 minutes longer than the train between Bristol and Gloucester. But some people travelling between the two cities wouldn't mind that much a little longer journey. And in the case of Broadmead/central area of Bristol, it wouldn't really take that much longer anyway. Would be about the same time really. What with having to get a bus from Broadmead/central area to Temple Meads, and allowing enough time to get your intended train.
Would be a shame if passenger volumes don't pick up and the service gets axed.