Greg - You Are missing out big time! It is a wonderful place.
Ace - The Lafayette is currently in the Roundhouse. I had the pleasure to give it a good look over. It is still certified to operate under steam and hasn't been run for a few years as far as I know but will likely be running in 2013. A neat engine to see, especially with the Imlay cars.
The William Mason, the oldest operating steam locomotive in the Western Hemisphere is not on display and likely will not be for some time. It is due for it's 15 year overhaul and is at the museum's shop about a half mile from the museum complex which is not open to the public.
Of other note at the museum, much switching has been done to pull out a few pieces they've kept hidden away recently. The operating B&O RDC is on display, the MARC 1 observation, WM F7, B&O Passenger GP9, among others are on display. The large C&O Steamers on display in the front parking lot have been pulled out and replaced with other equipment out front. The steamers are stored in a spot not accessible to the public and really not visible either. They are being stored there until restoration work can begin but volunteers say "don't expect anything for sometime".
All locomotives damaged in the roof collapse have been restored and are on unrestricted display except one which is still being worked on at the shop. The engineer on the train told me to expect an increase in use on the B&O Sunburst GP30 and Chessie GP as the red ex New York Central switcher has thin wheels and is being used as only as a shop switcher unless needed on the train ride. It has held down train ride service almost constantly since it's arrival on the property during the museum's restoration from the collapse. The MARC 7100 NPCU F unit is used somewhat regularly on the east end of the excursion train. He also mentioned a full reenactment of the Lincoln funeral train, complete with the Mason pulling period rolling stock upon it's completion of it's overhaul. The St. Elizabeth 0-4-0T #4 will be running next year during the annual October steam weekend and the occasional test runs. It is currently in the museum shop but may be moved to the Roundhouse later in the spring upon completion of it's annual work. The Mason won't operate in 2013, the Tom THumb and/or Lafayette will be running.
I was also happy to see much display engines have their headlights and marker/class lights lit up which was recently done.