It's very good up to about series 5. From season 6 onwards I found it started to grate that these people still hung out and did everything together, including having relationships within the group. It began to get a bit oppressive and disturbing, in fact! And too many of the storylines started to depend on one or other of them reacting really, really stupidly to situations. Yes yes yes I know it's just a sitcom but you have to have one foot in reality and be able to have some sympathy with the characters. There was a particular kind of comic spark it had up to series 5 that it lost after that. It also developed an over-reliance on the clipshow format.
But on the plus side, those first 5 seasons have some wonderful comedy, great acting and brilliant writing - the cringe-inducing "London" episodes aside.