The series has always been and will always be formulaic, but as long as the cases themselves are different, offering new explanations and stuff each time, I'm fine with it.
Besides, at this point in the series, the characters start poking fun at the various formulas. I think this set contains the first episode where Megure asks Kogoro's group "why is it that every single time there's a murder, you're randomly here?"
I recommend everybody get season four for the new episodes and to support the series. Season five's set for release already, but we won't get a sixth set if sales are low.