MBTA Silver Line

As a follow up to my BRT post, I want to critique my current ride on Boston's fairly new airport connector. It leaves South Station, the main train station and goes to the airport, which is a great link to have. It begins underground with full right-of-way and runs on electricity. After that there is a brief above ground segment where the bus passes through a couple signals. I'm not sure if it has it's own lane there, but probably does. It does cross traffic at one light, unfortunately. The bus then tunnels on a nondedicated lane (running on diesel) and circles the airport gates.

Pros:
Almost predictable arrival time, but airport traffic could delay it.
Partially electric and partial right-of-way.
The fare is part of the rest of the T. This is crucial. You don't have to pay on the bus or pay separately from the trains. I really don't think there should be an airport surcharge like so many other cities have. The biggest payoff is preventing driving, not collecting revenue.

Cons:
Manually controlled on narrow right-of-way. That seems a little bit problematic.
At least one red light that crosses traffic, cresting a variable length trip.
Handicap users are inconvenienced by the usual special bus loading procedures. Special ramps on the platform could help this, but you still have to secure the passenger.
The bus stops to turn off the electric engine and start up the diesel motor.
It's still an uncomfortable bus.

To me this bus is an acceptable solution. I'm just as happy with it as the alternative blue line train that requires a short shuttle bus connection from the airport station. I do wonder why in both cases a subway couldn't go all the way to the airport. At worst it could come in on an elevated track. I guess I'll have to go check the planning documents.