I can't address possible temperature control improvement as I don't know how well the 90s vintage units did. But the factory web site and the myriad of youtube videos indicate that it's quite good. The upward hot air flow is swirled by a turbine blade-like diffuser that's supposed to eliminate temperature variances across the grates. That seems as though it might be a bit of a gimmick to try to differentiate the unit from competitors, but I figure that it can't hurt.
Same with capacity. I suspect that it's improved over the 90s UDSs because many of the internal pieces seem to be new developments. However, most competitors have similar. Hunsaker's grate attachment method is different from the others' and I rather prefer it but it makes it impossible to use anything but Hunsaker internals.
The air intake is on the flat bottom and is adjustable, although the factory instructions say to make the final temperature adjustments with with the exhaust damper.
The fire basket is typical except that it's on short legs.
I, too, originally thought that the temperature gauge at the exhaust is unusual, but it matches the location of my kamado's gauge and it seems okay.
I don't care for the lid shape—it holds water. But I like the way the hinged lid lifts and isn't loose. That should reduce paint chipping.
EDIT: Messing with photograph size.