I think that a government that could work together with some semblance of bipartisanship would be good, on the other hand I completely understand the position politicians that would not normally make such a gesture doing so because it is Donald Trump in particular. I don't really know what would be better - unified solidatiry in just showing up no matter how distasteful he is, or making a point by giving it a miss in decent numbers - but ultimately I don't think it is that important.
One thought I had with regards to bipartisanship, as people start to wonder how the Democrats should act as opposition going forward... this election, America essentially voted that bipartisanship is irrelevant. The Republicans in Congress took obstructionism to new heights (most notable is the Supreme Court nomination which the Senate refused to even vote on), and they retained their majority and won the presidency. If you want any politician, Republican or Democrat, to think that bipartisanship is important, then sending the same people back and giving them even more power does not work. All that shows is that the strategy employed by the Republicans in recent years is the way to be successful. If the Democrats start doing the same (obviously they will not be able to do so effectively with minorities in congress, but if things change in 2 or 4 years...), then yes you could accuse them of hypocrisy for doing what they criticised the Republicans for. But on the other hand, they would simply be doing what the voters have shown is an acceptable and potentially successful approach.
So whether it's small symbolic gestures like skipping an inauguration, or something more meaningful further down the road, I think that we probably will see a lot of things that "People criticised / would have criticised Republicans for when it was Obama!" Which is a shame, and will of course perpetuate both sides doing the same thing. But on the other hand, the election essentially endorsed that attitude (along with various other things), and showed that the Democrats' whole "When they go low, we go high!" rhetoric was not going to be successful for them.