I bought this app in preparation for the TEDxHouston conference last month, but have really started using it more & more in my daily notetaking at the office.
Penultimate is essentially an electronic sketchpad app for the iPad. It allows you to create & store multiple notebooks, each with as many pages as you need.
You can write notes directly onto the iPad's screen with your finger, however I opted to pick up a Pogo Sketch Stylus from the Apple Store and have been rather pleased with the results. This makes for a more natural "pencil-to-paper" feel when you're writing.
Working with the foam-tipped stylus, I find it's best to write bigger on each virtual page within the notebook, since small letters aren't as precisely interpreted by the app. Yes, you'll end up with more pages in your notebook if you write bigger, but they're virtual pages.
Perhaps my favorite feature is that you can e-mail your notes directly from the app. If the note you want to send is only a single page, it will export as a PNG file. If you want to send an entire multi-page notebook, it will export as a PDF file. I utilize this feature to backup my notes to Google Docs.
TUAW has a more in-depth review here:
http://www.tuaw.com/2010/04/19/tuaw-review-write-and-organize-handwritten-notes-on-your-ipad-w/
For more information from the developer, check out their site below:
http://www.cocoabox.com/
