I read the last Gotham Central trade and liked it just as much as the rest of the series. I love the down on the streets of Gotham point of view and the art is just superb for the series. I like the characters and the use of the DC universe as a spectacular aspect that gets thrown in every now and again to remind the reader why these average joes are always wound a bit tighter than they should be.
It's as good as any cop drama, although the Dead Robins storyline did pull a bit of a cheat as to who was guilty and why. I don't completely hate that but I'm not a huge fan of it either because it feels like a cheat, moreso if it is used too much in a series.
What I love most about this series is that it can only really work as a comic book. It simply wouldn't work in any other media because the spectacular superhero aspects would just be too jarring or look too incongruous with the man-on-the-street presentation. In comics, it doesn't matter because nobody is real. I'm a bit sorry that the characters had to leave all too soon because this was a fantastic set of comics.