Some of his documentary style work is very good. I enjoyed Re:Brand back in the day, plus his recent visit to Oxford Uni (which was supposed to coincide with the BNP visit but they pulled out) was also good stuff. He also travelled the same route across the USA as Jack Kerouak and made a very good documentary on that. As a social observer I think he's a talent. The quality of his comedy work is largely dependant on the script, some works, some doesn't so much. I'm not that keen on his radio work, he spends a lot of time repeating what his guests say, but suffice to say it's better than anything on Radio 1 at the same time. Big Brother stuff I've no idea about.
I borrowed his autobiography from my missus and it was quite enjoyable, though my sister described it as "..a bit 'Me, me, me'..." when she borrowed it later.