I love Eureka. I don’t care if their science is anywhere close to right. I like the way the play with possibility. They have done time travel in a way I believe, had a Groundhog Day episode that did not feel like a copycat, and managed to redeem the characters you thought were bad guys.
The biggest plot hole is that everyone was uber paranoid when the sheriff first showed up but since then, a major character randomly arrived in town, and the sheriff’s sister and showed up, with no one seeming to mind that she learned the town’s secret.