I pass service 34 every morning on the way to school and this is just a few observations I have made over the months.
As i'm sure your aware of the service does have special route branded buses, these being the 3 '56' reg Enviro 200s. There also used to be a Mercedes 709 which used to operate just infront of the bus to Derriford, which would terminate at Milehouse but this has now ceased as with many of these 'short' services, which were first put in place because of bad timings with the Cremyll Ferry departures and arrivals.
Recently punctually on the route has been much improved and this is why only the 1 bus operates on most services now. Though bus types used on the service, at least on the particular one I see do vary. It is now quite normal to see one of the '08' reg Enviros on the 34, and also one of the newer Darts. But today was a little reminder of the past, this being M127 HOD. Step Darts used to be the staple bus for the route, but now obviously have been replaced by the newer vehicles. It was much nicer to see a good strong steppy on there for a change, the sound is just that bit nicer compared to the Enviros! I do wonder why it is a common occurrence to see one of the '56' Enviros on services such as 41/2 though. The buses were funded and bought just for the route, and yet they are often used on other PCB routes. I'm sure the users are not complaining having an even nicer bus on route, though it does seem to destroy the point of having the buses route branded, as in many cases nowadays.