Welcome Mogrith. I'm a very satisfied Kindle user.
Biggest down-side to the Kindle is that you don't have to wait until you can connect it to your computer to buy a new book. That means you have to keep tight control of your impulses! Fortunately, there are SO MANY books available for free or for a very reasonable per-book price. Since you read SF, check out the books from Steve Jordan at
http://www.stevejordanbooks.com/ He offers one novel as a free download so you can decide whether you like his style or not. Then, the rest of his books are available in bundles with extremely good prices.
I'm plunging into classics that I probably *ought* to have read in the past, but never got around to. It's amazing how many books are available here at MobileRead through the generosity of fellow forum readers (and posters). I'm trying to figure out how to get BookDesigner to behave and then I'll be posting some books as well.
(Note to JSWolf: after holding a PRS505 at Border's, I know that I could have been happy with it if I didn't have the Kindle. Biggest down-side to the Sony is getting recent releases for less than $10 apiece. Amazon appears to have a big advantage there. But, when I have some discretionary funds, I may buy a Sony just because I'm a gadget geek.)