To all those that think Sumday is rubbish: It's not. It's just not as unpredictable and epic as the first two, but it's still full of brilliant pop songs (even though it can be a bit repetitive).
However the first two albums are beauties, nonetheless. I don't have Fambly Cat and I'm not convinced it'll be worth getting judging by what people have said.
Also, He's Simple, He's Dumb, He's The Pilot = what a song.