The first two series were brilliant. I bought them both on DVD in 2006.
I didn't like the new series. The jokes weren't the same; it seemed slightly mainstream (i.e, The Horrors, Electro and all that.)
Maybe The Boosh are becoming too well known, and thus, it doesn't seem great anymore. Everyone kept on about it when the new series aired, and last year, when all that Emo nonsense came into fashion, people just kept on and on about The Mighty Boosh all the time!
Bollo looked and seemed really different.
I can't decide what it is that made this new series pretty crap, but the series 1 & 2 are better.