A general note on stylus accuracy
The right pull-tab exposes the various annotation tools.
There is a pencil for free-hand marking up of the document. Unfortunately this tool does not support the stylus-width control of the Tegra Note. To be fair to the Note, iAnnotate doesn't seem to support pencil widths at all, so I doubt a tablet with an active stylus would have an advantage.
Next is the annotation button. Touch the button, then touch a point on the PDF document and you can type in an annotation. These are the annotations that can be navigated through using the tool in the left pull-tab.
There is a highlighter for highlighting text. Note that this will only highlight text and cannot be used freehand like the pencil tool. The advantage to this is it is very easy to accurately highlight text. The disadvantage is that some PDF files are scanned without the use of OCR, so the PDF is actually just a "picture" of text.
There are a couple of buttons for scroll-lock and fit-width, and the last button on the toolbar is a toolbox button. The toolbox button exposes even more tools. In the toolbox you will find strikeout and underline tools that operate much like the highlighter. There are tools for adding, and navigating through, bookmarks. It also has buttons for emailing the PDF, the PDF with annotations, or just the annotations.
If you regularly work with non-PDF documents, iAnnotate PDF won't be of much use. Also, you cannot use iAnnotate to add or remove pages within a PDF. The interface does require some accurate touches, so in this regard the Tegra Note was tremendously useful. The fine tip of the stylus made highlighting, drawing, and placing bookmarks and annotations much easier than depending on finger touches or constantly zooming in and out.
iAnnotate will stay installed on the Tegra Note for now, but I will keep looking for a good Notability alternative.