Just to clarify. D4500's are the older buses.
D4505 *note the 05* is a new bus type.The D4505's have the G4500 style headlights, and the J4500 style running lights on the top cap. I got to ride one of them recently on my return from New Orleans to Lafayette, It was a nice ride. They ride better than the older D4500 units, which I find a bit harsh. Although GLI doesnt tend to maintain their equipment very well. I recently saw one of their 2009 Prevost X-3 units, and it looked like hell.
Along with the Prevost X-3's that GLI is using now. I got to ride one of these from Binghamton NY, to Syracuse to catch the LSL after visiting my girlfriend. The X-3 rode well, but the seats werent all that comfortable, and after speaking with the driver, he didnt find the seats comfortable either. Although I guess having gotten used to the Amtrak seats, no bus will ever be that comfy.
An updated fleet for Greyhound are the D4500's *older units, currently being refurbed by GLI with the new paint scheme and seats* G4500's *blech, I hate these* , D4505 *new buses*, Prevost X-3 *new buses*.
The G4500's will be replaced as well, as there have been issues with that series. Fires and whatnot. Every driver that I know personally hates the G models. They only drive them because they have to.
They are slowly replacing the fleet with the newer buses. The new D4505's are going to replace the older D4500 units.
Here in Lafayette, Im seeing more and more of the D4505's and Prevost X-3's as they phase out the older units.