Basically, the series focusses on two characters: freshman Hato, who only attends the circle when he crossdresses as a girl (to be 'one of the girls'), and Madarame, who is slowly drifting away from his life as part of Genshiken. Again, the characters are shown with some sort of compassion: the obsessive weirdness is not hidden, but it's not to make fun of. And in the case of Hato and Madarame, there are some complex inner processes at work that have led them to where they are now.
I enjoyed watching the series, but as we progressed I realised there is not really a point to the story anymore. There is not a story arc that is shown and then resolved -- it's just the characters that we know and the characters that are introduced continuing with their lives. And while that's interesting (we haven't watched three Genshiken series because we thought it was boring), I felt that the writers could have done more with the source material to make it more of a story instead of some otaku-version of 'slice of life'.
Still, I liked it. And I'm pretty sure we'll watch a following Genshiken series if and when it gets made. I'll give this one a 7.