Well, I finished it. All told, I think it took me two weeks, which is, for me, an awfully long time for any book. I did read a couple of other things at the same time, but it was all fairly light stuff.
The first and most obvious question is, I think, "What is so pathetically wrong with the way that books are sold in this country that a novel reputedly written with a fountain pen, taking place entirely between 250 and 350 years ago, involving various and sundry historical events and persons, is going to end up shelved under Science Fiction/Fantasy in most bookstores?"
But the ghettoization of literature is not something I feel any great need to rant about right now, so please just take it as read.
I think the writing is better than Cryptonomicon, which seems sometimes too clever for its own good, and much, much better than Snow Crash, which is far too precious.
The characters are compelling and human, if at times improbable. The settings are interesting–both in terms of physical location and thetime and events surrounding them. Overall, I enjoyed it, but at the same time, Neil Stephenson seems to have a deep-seated need to try and address everything under the sun all at once. I can imagine a lot of people who would never consider slogging through such a book, with the promise of two more to follow, almost certainly of similar heft. At times I wasn't even certain I was up to it.
So, ultimately, it's worth reading, but if I were restricted to a single historical novel by traditionally other-genre author(s), I would go with Freedom and Necessity.