> new (weird, not sure why) latency in tuning in a channel after the DTV transition,

Because with analog signals the tuner just had to tune to the correct frequency and at the next vertical blank sync pulse on the video signal the display could begin drawing the picture.

With digital, the tuner has to tune to the correct frequency, then the digital decoder has to sync with the transport stream (fairly quick as TS packets are fairly small) then it has to start watching for a key frame (because without a keyframe the decoded images would appear to be static) and depending upon the compression settings from the transmitter, keyframes might only be transmitted every few seconds, so there's a multi-second wait for the next keyframe to arrive, then the display can start drawing the pictures.