If you're going to watch a movie from Gosei, and Zeo will back me up on this, watch Shinken v Goseiger. It's by far the best and one of, if not the, best Sentai movie ever produced.

Is anything from Goseiger worth watching?

I'm going to save that opinion until I finish the series.

Ground Gosei Great. And it's a damn impressive combo. To just be a 2 mech combo it's very impressive.
Actually they do reference it. In epic 38 they summon Gosei Wonder to save that bullet train going across the bridge that Metal Alice blew up. They briefly flash to the movie footage and then the cards appear to summon it.
Shinkenger Vs Goseiger is still one of the BEST team-up movies there is.

I've been hearing that a lot. I guess I'll take your word for it and watch it. When does it occur? Or will I get previews for it to indicate when I should watch it?

Shows how long ago it was I watched Goseiger :lol

When the previews start popping up is a good time. It takes place after the Yuuma have been around a while. Around Epic 30 should be safe.

Currently pushing through a slog of episodes. Nothing much seems to be occurring. Some mild character development here and there, but nothing really important or major. So far, the only thing new is during this laughter episode, where we find out that Gosei Knight is willing to not be a colossal dick for 5 minutes.

Lots of stuff going down. Buredoran died, Makuin and Kingugon pulled a double-double cross, Gosei Knight continues to not be an ass, and the Goseigers are...Yeah. They're there too.
But, during my little marathon of this series, there is nothing stronger to kill my drive to keep watching than an Eri episode. It's strange, I don't even hate the character. I think Eri is alright. But her episodes are just...Bad.

Just waiting for Kyoryuger.