A fun finale, but I don't get the part about how they were stranded in 1916. Didn't they still have their keys with them? Heck, Gary was able to build his own door in prehistory and it somehow worked. (Also, the fact that Gary's hair and beard grew proves that his human form is a physical transformation and not a hologram, though I guess his physical relationship with Gideon proves that too.)
This was sort of an intimate finale in a way, focusing almost entirely on the team, with Alan and Booster Gold being the only significant guest stars. And it was largely about paying off character arcs. Sara and Ava get pregnant (cute way to use alien biology to let them do so without a donor), Sara loses her invulnerability (for good?), Nate loses his power and retires, Zari gives up her totem (though Behrad still has his, I think), Gwyn rescues Alan, Gideon comes to her senses and reaffirms her daughter/mother bond with Astra, etc. I think my favorite payoff moment was Astra finally succeeding in her Waverider restoration spell that she failed to achieve at the start of the season.
Booster Gold is a natural fit for this show, and he made an effective first impression. It'll be interesting to see how things shape up with him next season. (Doesn't the comics character have some kind of link with Rip Hunter?)
By the way, I noticed a "Superman created by Jerry Siegel & Joe Shuster" credit in the end titles. Why would that have been there? I didn't notice a Superman reference.