The Kindle has 2GB storage. Reading PDFs is no problem. You can plug your kindle in and just use it, on both MAC/PC as an external hard drive and transfer all the files you need. It will also play mp3s, although just in the order you uploaded them. I converted my PDF files to the Kindle format, but I think you should be able to just transfer your PDF files.
The US kindle has a web browser, so you can access the web if you have a wifi connection.
Here are the dimensions (scroll down a little, the bigger one is the US model.)
http://www.amazon.com/Kindle-Wireless-Reading-Display-Generation/dp/B0015T963C/ref=dp_ob_title_defYou recharge it through your USB port. The rechargeable battery holds up for a week of moderate use (no music or audiobooks, and you always can disable the wifi connection to preserve power if not needed.)
Cases are optional, so you better order one with it if you get a Kindle.
Color screen: Nope. And, that is a good thing. The text is displayed with electronic ink, there's no back lighting (you can't read in the dark,) and no glimmering. Text is sharp and very easy on the eyes even for long reading times. No scrolling - it turns the pages.
I really enjoy mine, but of course I'll wait for the Apple one, too. But who knows when it comes, and in the meantime, the Kindle is my way to go.