Personally, I think his Bigend Trilogy is every bit the equal of his Sprawl Trilogy. Extraordinarily perceptive about the contemporary world and the way our social lives have changed over the last 15 years, in both scope and in experience.
I'm not crazy about his Bridge Trilogy, though it has its moments. Overall, I think those were his weakest books.
The Peripheral also sort of underwhelmed me. I liked the near-ish future, with the look at how hopeless redneck-ville would be affected by technological and economic trends. There's a mix of the past and the present (our present and our future) in those bits that plays quite nicely and feels very real. His far-future London, though, felt very under-imagined. I don't think it went far enough. I also think he tried something interesting with hicks being just as dangerous as the sophisticates, but it didn't quite gel the way I think he meant it too. Still, it's not a bad book, it's just not as good as I'd hoped.