I'm not that into busses but my friend drives on the 192, so have spent alot of time on Enviro 200s...
Couple of problems, one was noticed by another driver I know, that is that as the disabled ramp is, (it was described), 'underneath' the bus as opposed to inside, when they were first introduced to the route, (as a replacement to the PDL busses), I know of at least two drivers who drove to close to the kerb and hit the ramp on it.
Another problem that has come to light recently is that one of the roads that the 192 goes down, (Fotheringham Road), has speed humps. The problem is that the bus isn't raised soon enough and therefore if the driver is driving too fast or too slow the bus would clip the underside of the kerb - the 192 is now on diversion along that part of the route.
Anyway, I find the seats rather comfortable, the bus is quite spacious, there is space for two buggies and a wheelchair, (although the arm is a little weird).
Although there always seems to be a fault with the EN busses, (but admittedly thats with iBus)!