Pointless filler. "The Naked One" is what it should have been called. To fit with similar-themed Star Trek episodes The Naked Time and The Naked Now. Hell, I wonder why they didn't have someone like I don't know, Eli prancing around the ship shirtless waving a sword around.
But yeah, this storyline has not only been done on Star Trek a bunch of times, I'm pretty sure other sci-fi has done variations on it. This episode offered nothing new to this particular trope, nor did offer any new insghts to SGU.
And it really was a letdown seeing the Sombreroids coming through the gate was just a hallucination. Mind you, I had this predicted after last week when they didn't board the ship then. I know spoilers for the rest of the episodes this season, and there's no way the Sombreroids could fit into that, so having them in the hallucination was the only viable option. Although, I was hoping that maybe the whole thing would turn out to be Sombreroids already on the ship and they were torturning the crew, but sadly this was not the case.