Several authors and would-be authors have asked us what it's like doing a book with a print-on-demand publisher like Lulu. Overall, we're pretty pleased: you have complete control over content and schedule, and since traditional publishers are pushing the work of publicizing technical books onto authors anyway, the only thing you really lose is professional copy-editing. You can always hire a freelancer to do that, though (which is what traditional publishers mostly do); if you're interested, Amy Brown (my co-editor) now has some time...
There are some caveats, though. First, you're entirely responsible for creating electronic versions of your book, and it's much harder than I had expected. A couple of volunteers have been working steadily since Monday to produce e-pub and .mobi versions of AOSA, and they still aren't right—tools like Calibre, kindlegen, and eCat do a mediocre job quickly, but doing something that looks professional turns out to be much more difficult than it should be in the early 21st Century.
Second, while Lulu and other print-on-demand services cross-list at Amazon, Barnes & Noble, and other outlets, the royalty structure is—well, if you have a look at the http://aosabook.org home page, you'll see the breakdown.
A third complaint is that Lulu won't ship to a post office box: they say, "Because our expediter won't," but that just begs the question of why they don't use a competent expediter. It doesn't affect most people, but it's a real inconvenience for those it does. Please let them know if it's a problem for you (or if you bump into Bob Young, ask him why they haven't fixed this yet).
Finally, we have run into cases where it's clear that Lulu's right hand doesn't know what it's left hand is doing. Right now, for example, we're trying to reconcile a complaint from Lulu about missing fonts in our PDF with their simultaneous report that our uploaded file is fit for use. I've had similar problems with all four of the traditional tech publishers I've worked with over the last 20 years, though, so while Lulu isn't better, it isn't really worse.