On the steel breeze is one I regret: I really should have known - indeed, I really did know - better than to start reading it. I'm moderately pleased I had the sense to stop reading before the end; about 3/4 of the way through. But I regret not stopping earlier. Its another interminable part of his series about not-very-interesting-people that began with Blue Remembered Earth (see my review of that). Its all a bit "oh, I've got a storyline, I'll spin it out into another book, because I'm pretty well out of ideas".
Other people liked it more, so you could read them if you want a different opinion. But even there you can see some of the doubt I have.
[Note: I wrote this on 2014/06/20, but I've arbitrarily pushed it back a few months to about when I read it.]