It's a throwback to another era, probably about the 1950s - a little train trundling along, stopping at halts in little villages, picking up people who often know each other, and the guard, and dropping them off to do their shopping or errands in the small towns along the route.
The valleys around Knighton and south of Sugar Loaf are the most scenic, though the rest is pleasant rolling countryside. There has been some lineside clearance done during last year's closure, to reduce the effects of leaf fall. I haven't travelled the line since, so I don't know if that has improved the views. In good weather there can be wide open views, but in bad weather you won't see much beyond the carriage windows.
Most of the stations are well kept, as the line's user group has local station adopters who keep them tidy, often with floral displays in summer.
Rolling stock isn't great - the 150s are reasonably spacious but the seats are poorly aligned with windows, while the 153s have poor legroom, especially if you end up sat over a heater.
Train crews swap units where the services cross, either at Llanwrtyd or Llandrindod. At one time there was a regular trolley service south of there, but I certainly wouldn't rely on that still being the case.
Personally, I think it's well worth riding along just for the unusual experience of a long cross-country branch line, but I can see why others might not agree.
