Series 3 is sort of uneven - three standout episodes that are strong enough to overwhelm the lazy, self indulgent strand running through all six. The main problem for me was that they brought to the fore those wonderful details that added unique texture in series 1 & 2. For example, crimping. Before crimping had a name, it was something that cropped up every now and then in a natural, brilliant sort of way. In series three there's an entire episode dedicated to crimping. Knowing it's something that can be taught, can be practiced and even copied just sorta cheapened it. The same goes for the Council of Shamen, and particularly Tony Harrison who's been transformed into a hard living drug fiend.
The other big problem is that the Boosh now inhabit the same space as a lot of the real world, and it's not a particularly great one - it's full of Camden posers. In Party, they're even told by Vince that they're the chosen people. They're arrogant, shallow body fascists. That was charming when Vince was the only one and it was taken to a surrealist extreme, but now it's just irritating. That's one of the bigger problems - Vince has stopped being lovable and the friendship between him and Howard descends into point-scoring and spite.
The standouts are Eels (the Hitcher remains reliably nasty), Journey to the Centre of Punk and especially the Crack Fox (definitely Julian Barrett's best turn and an effective comedy/horror mix). Even those have moments you'd rather weren't there, just as the weaker episodes have moments you want to savour.
Mighty Boosh 3 is not as good as their previous work but it's still better than any other comedy on British TV. I reckon series 4 will be a vast improvement and in the meantime, it's still not that bad. They just set the bar so high before that it was hard to top it the third time out.