You got a good deal if you bought your Kindle for $315! I bought one for $399 and the second for $359. I'm loving my Kindle. I justified the price (though I spent my mad money and didn't really have to justify it) by telling myself that each bestseller would be $9.99 from Amazon and I'd only have to buy 40-50 books before the Kindle was paid for in the savings off the hardback book price.
Though I've bought about 2 dozen books (only 10 from Amazon so far), I've also been reading eBooks that were provided free on such sites as MobileRead, Feedbooks, ManyBooks, Munseys, and Baen. If you like Science Fiction, be sure to check out Steve Jordan's books at
http://www.stevejordanbooks.com/ Steve offers one of his books for free and then absolutely terrific prices on the rest.
It is my intention to dedicate my Kindle to recreational reading -- and not use it at all for academic or work-related books -- so I'm not going to mess around with trying to come up with some way to get PDFs to work on it. I wish you luck.