Seriously, clicking up down with channels, there is very little of that slow feeling blank out / blank in thing that is so annoying.
I'd love to have an OTA receiver go into something like this at my house with this simplicity and speed (I did HD Run or something once and the hoopjumping was high and quality low).
I imagine cable is pretty similar, but I suspect most cable boxes are more capable than tuners in tvs, so they may be running multiple tuners, and I think there's more of a chance of subchannels being useful, too.
With digital TV, several channels are multiplexed into a single broadcast frequency, so channel hopping is sometimes OK even with a single tuner.
It's definitely a nice weekend project if you are serious about cutting the cord and are in an area with decent OTA signals.
I will say though, that MythTV does have the annoying "slow channel switch" issue, since it literally needs to buffer some video data before it begins to play.
They skipped ATSC 2. There were a couple broadcasters experimenting with newer codecs on ATSC, but I think that mostly fizzled out.