I was thinking of taking this train from Philly to Pittsburgh over the weekend, staying overnight and coming back the next day mainly for the train ride (I've already seen Pittsburgh and its sights). Is it worth it? I assume the train is turned around in Pittsburgh? Will I look like a nut if I come back the next day on the same train (with the same crew)? That is does the same crew come back from Pittsburgh?
I think it is definitely worth it. You'll ride the Pennsylvania Railroad's "Broad Way" main line with scenery including the venerable Main Line suburbs of Philadelphia (clever name), the farms of Lancaster County, the Susquehanna and Juniata Rivers, the Allegheny Mountains, and the industrial approach to Pittsburgh. Highlights are the Rockville Bridge crossing of the Susquehanna and, of course, Horseshoe Curve as you climb toward the Allegheny summit. And for train watching, The Norfolk Southern's line west of Harrisburg is big-time railroading at its best.
By all means, take the ride. It is one of Amtrak's most overlooked scenic trips. And consider going Business Class at least one way. It uses a former Metroliner Club Car with 2-1 seating. It's a great way to stretch out and enjoy the view.
As for appearing a "nut", try this on for size. Two years ago an airline had an early year promotion offering triple preferred miles for each round trip taken in January. So, I flew from PHL to Manchester NH (for $40), said goodbye to the crew as I got off, sat in the boarding lounge for 30 minutes, and then said hello to the same crew as I boarded the flight back to PHL. They did give me an odd look. I did that two weekends in a row. With an overnight in Pittsburgh, even if the same crew is on the train back, it won't seem all that strange.