One of the nice features about Barnes & Noble's PubIt system is that it includes an offline app (Nook for PC eReading) that you can use to preview your manuscript without having to click through page after page of your book in a Web browser, which can be agonizingly slow.
Once your book is uploaded, B&N promises that it will be live within 24 to 72 hours, and the company had Five Stars! up faster than that. The listing page is a bit spare--even with the five review blurbs I uploaded--and the book is unfortunately not linked to its paperback counterpart, which is also available from Barnes & Noble.
Still, the process is simple, and the sales possibilities are enticing.
The 70% commissions from Apple iBooks are dandy, but before you get too excited about your book being available for the iPad, be aware that publishing directly through Apple requires you to have a Mac. Die-hard PC owners can use an aggregator to make an end-run around this issue (see below), but the commissions are lower if you do.
To get started, sign up for a Paid Books Account (you can offer your book for free via a different mechanism), using your Apple ID. Fill out the personal information requested, and wait for an email reply: Apple has to approve your application. Once you get the okay (my approval took a few days), you have more paperwork to do, including a bevy of additional forms to fill out.
With that complete, you must navigate additional hoops. Apple requires both an ISBN for your book and your manuscript in ePub format. While other providers will translate a .doc file for you, Apple won't. You can use any of a variety of tools to convert your book to ePub format, or just use a tool that one of the other sellers made for you (which is what I did). Then, using the iTunes Producer software (here's where the Mac comes in), you can finally publish your book. But you're not done yet: Apple has another "quality review" at this point. A week later I was still waiting for my book to be live on the iBookstore.