I have only used business class once on the Carolinian and it was fine; I can't say it's enormously worth it unless the business class cost isn't that bad when you're traveling (or if you do BidUp, which is I think what I did). That said, it was a short trip. I can't tell if there's actually most seat space/comfort--maybe a little? Others can chime in there since I've only done BC once. It was quieter for sure than coach class.
The main thing I'd say from my experience is that the Carolinian is often incredibly full these days, which is good for Amtrak, but rather bad for general atmospheric noise/chaos/condition of bathrooms/cafe car lines, etc.. I've worked remotely from the Carolinian about 3 times now, and it was (naturally) harder to work when the train was really full. Also, I find the space and comfort of the Amfleet I cars used on the Carolinian to be worse than the Silver Star's Amfleet II coach seating. I live in the Triangle, so I often go to Raleigh and take the Star north instead of the Carolinian. So perhaps worth it for such a long trip to have a tish more space and less chaos?
McLeansvilleAppFan posted while I was writing, and I will say that my last Carolinian trip in March, I was stuck next to a (very kind, polite, and friendly) young guy who was unfortunately a smoker and probably also a weed vaper, and the smell + being closer to him in the Amfleet I coach seats wasn't the best!