For me the number one issue with Amtrak's Business Class is that I rarely know what I'm going to get until I'm already on board. Sometimes it seems like a good deal while other times it seems no different than coach but with a higher price. I don't necessarily need or want Business Class to be identical everywhere across the network, but having a well defined and consistent standard for each route and corridor would help to clarify the sales pitch and possibly sell me on an upgrade. Otherwise I end up assuming it's not worth the trouble unless someone proactively recommends it thanks to a recent trip of their own.
With 2 exceptions (at least in the east, with which I am more familiar), you do get something better than coach. The two exceptions are the Pennsylvanian and the Palmetto.
Other trains are as follows:
NE regionals, BC seat is ~50 in pitch as opposed to the 39 inch pitch in coach, as well as there being curtains to shade your eyes from sun glare or station lights, very important if you're taking 66/67 and ant to sleep. Oh yes, and you get a free drink, for what it's worth, but at least the drinks are full size now, and presumably the ice is also included.
Vermonter/Empire Service/Downeaster has the 2 x 1 club car seating. 50 in seat pitch vs 39 in coach, as well as curtains, and, of course, free non alcoholic drinks.
Carolinian (which is longest ride one can take in an Amfleet I coach, if you ride from end to end) has 50 inch pitch Amfleet I BC (in other words, it's basically a Northeast Regional BC with a car attendant.)
In all of these cases, you get more legroom and a less crowded car (most of the time), which increases the single traveler's chance of not having to deal with a seatmate.
The real marginal value propositions are the Pennsylvanian and the Palmetto, because the physical layout of the Amfleet I BC car is more or less the same as that of the Amfleet 2 LD coach. (Same 50 in seat pitch, same curtains on the windows.) What you're really paying for is an increased chance that the BC car will be less crowded, and thus you don't have to have a seatmate. If you're traveling with someone, well, that's not much of an advantage. I ride BC on the Palmetto, at least on Saturdays, the coach section gets pretty filled up by Florence, whereas in BC, it's nice and quiet all the way north. Well, I'm taking it on Saturday, I hope I don't have to eat my words.
Oh yes, and you get a 25% TQP bonus on your AGR points.