It's a trail right up your alley, Tom. Mostly flat with some long grades on the eastern side, but just chug along stuff, nothing steep. It's all gravel but great on a tourer. Lot's of B&B's and places to visit.

Biggest issue is getting to the start. Us easterners would typically park a car in Cumberland then get to Pittsburgh and ride back. As BTW, the GAP is complete thru to downtown Pittsburgh as far as I know. So in theory, Amtrak is doable, except I don't think they can handle bikes from Cumberland to Pittsburgh. There is a company offering shuttle services as of last year. Here's a link:

http://www.atatrail.org/pv/shuttleservices.cfm