I've not seen season 5 yet because no network here airs the show anymore.
They went a long way with it, but they stopped.
At that point I already had 1-4 on DVD which I all loved. (5 isn't out yet)
So I have no idea what season 5 is like, but from what I've read here, I'm not 100% happy.
But I now read it's cancelled.
The last eppi won't be on screen till 2011!
Which sucks, cause that means it prolly won't be on DVD till 2012 and here in the Netherlands we're always behind on everything, so I won't be able to get them till like 2013?!? Source