Safari is now supported (this John Resig post was invaluable). The screenshot below proves it!
There’s also a guide to how far you are in the current section. It’s based on a percentage rather than an absolute number of pages (similar to the Kindle’s pagination indicator).
Update Feb 18: Key controls have now changed
n = next page
p = previous page
j = next chapter
k = previous chapter
Update April 3: IE 7 now supported (and possibly IE 8, haven’t checked).