Charles Stross' work can be really hit or miss for me. This book was enjoyable, but seemed almost rushed. I don't mean rushed in terms of pacing, but almost like there was a lot going on in his head that never actually made it to the page, which made it a far less thoughtful book than it could have been.
There are some interesting ideas in here, particularly the musing on how a society of robots designed to serve humanity cope with the fact that humans are extinct, and thus their primary purpose in life is obsolete. There's a lot of heady thought wrapped up in that idea, including questions of free will. There is also a lot to think about in terms of identity as each robot is based off of a template persona's memories and can trade their own memories with others of the same template. These difficult issues are discussed, but Stross seems worried that too much exploration of these existential problems would get in the way of the story, which results in some of these questions being simply glossed over, making them feel too much like simple plot devices rather than the central issues that they are.
One thing I will note here is that many of the robots (even the non-humanoid ones) have a particular fascination with sex. It's significant that Stross points out that as humanity attempts to make robots in our own image, it is only natural that they would end up sharing our preoccupation with sex as well.
To sum up: interesting ideas and an entertaining read, but not nearly as complex as it could have been. I had fun reading this, but on the whole I ended up feeling disappointed.