I guess I'm the first not to agree with anything.  There were some episodes that I felt were 'out there' 'off' or whatnot, but in general I'd have to say I'm sad I can't look forward to a next season.  I think near the end things started getting slippery but Season 1,2,3 were great.  4 was harder as they introduced new concepts - for better or worse, but it still stayed interesting.  In anycase, I enjoyed most of the series and celebrate that it ended before being slowly run down.
EDIT: Though this wasn't a series you could really skip a several episodes and think you can keep up.  It was one of the very few series that continue from episode to episode with a main storyline.