After a gruelling week, it's finally nominally over - all networks projecting the presidency for Joe Biden. A long election was always a possibility, but it's been exhausting seeing it happen in practice. It won't actually be close: Biden has the most votes of any candidate in history, and will have more electoral votes with more comfortable margins than decided the 2016 election. That said, there seem to have been two major misses along the way with predicting it: the midwest was a lot less Democrat than expected, so the key "blue wall" states (WI/MI/PA) have razor-thin margins instead of the comfier 5-10 point range that the polls were coming in at. Second, both Mexican-American and Cuban-American voters seem to have been a weakness for Biden, resulting in poor margins for him in Miami that lost him Florida (he did better than Clinton in the rest of the state), and in slightly weak performance in places like Texas, Nevada, and New Mexico (the Democrats held the latter two but Nevada is tight and the New Mex 2nd district went red). On the other hand, polls were pretty dead on in other places, like Georgia and Arizona where Dems slightly favoured in a tight race was absolutely the prediction and result - and the electoral map that results isn't too different to what one might have expected at the modest but not catastrophic end of Dem performance.
Also it's not over - there are two runoffs in Georgia which will decide control of the Senate, and which will likely favour Republicans unless they're too busy with Trump burning the party down on his way out. It's really hard to see what happens next to the GOP, and that's probably the biggest unanswered question of US politics right now.