I haven't watched a lot of Eureka... some when it first came out, and some more recent.... but in a way the two shows are pretty similar. I think Eureka deals less with aliens and supernatural things, doesn't it? But both shows are rather humorous and involve out of the ordinary things, including super science gone wrong. Middleman seems a little bit more camp and humor than Eureka though... and a lot of its characters are tuned more toward the alternatively cool.
If you haven't started watching it, I seriously suggest you do. It's on ABC Family at 10pm Eastern for the Americans.... and somebody's gotta be torrenting this stuff for everybody else..
It might take a few episodes to get used to the characters, but I'm seriously looking at this show to be another cult following type deal.