I have noticed that the input fields are displayed very large, (depth not width) when browsing with Apples Safari. This affects the username and password field and also the onscreen textedit box appears to type messages like this in. I would say the keyed font is probably size 16 on my Macintosh The rest of the site works really well though.
I use Apple Safari all the time and have never noticed this on any other site I have been to on the web. I don't think it is a problem for Apple, perhaps I will have a look at the page source and try and figure it out also