Saw it. Thoughts:
To describe it as "Trump bashing" is brainlet tier. Very little of it has anything to do with anything related to Trump.
The special is weird, in a good way. It drops you in expecting you know all about Harvey Birdman and feels like an inside joke they've spent ten years dreaming up. For example, there's a musical number with Phil and Reducto. There are points where you have no idea what's going on, and I think that was the intention.
Harvey Birdman having died turns out to be a part of the plot.
They got the original guy to do a new version of the intro song, and it's terrible.
Gary Cole sounds exactly the same as he does in the series. Colbert has gotten a little higher pitched in his delivery, and Paget Brewster sounds a bit too womanly for Birdgirl
Peanut is in it, with voice lines.
X the Eliminator is also in it, and Peter MacNicol still has it.
It's really hard to put a rating on it. It's both Harvey Birdman and it's own thing. So I'm going to go with "it wasn't what I was expecting."