Miscellaneous thoughts, in no particular order:
Assuming current results hold, Biden held all Clinton states from 2016 and flipped all three blue-wall states, Nebraska's 2nd C.D., Arizona, and Georgia (!). That's a very solid victory.
The polls were about four points off yet again. Is Trump just poll-proof? Did some Biden supporters not get out to vote because of Covid or other reasons? I look forward to statistical analysis on this in the coming months.
Democrats definitely underperformed in Congress. The biggest question moving forward for them is why and how to fix it. Voters across the country may have been tired of Trump, but they're not ready to embrace liberalism just yet.
What happens to the Republican Party now? Do they embrace Trumpism or resort to a more dignified conservatism a la McCain/Romney? Trump isn't going away. His Tweets will hold political power, for better or worse. And no, Trump running in 2024 is not out of the question.