I own both a Kindle and a Sony PRS, so maybe I can help.
1) When I am transporting the kindle, i wrap the elastic band around the Kindle and it stays pretty secure for me.
2) I remove the Kindle from the cover when I am reading from it. It can be read with the cover on, but as you've discovered it is a little awkward.
2) your second 2) Yes it got better for me after I got used to it. But the page turn buttons are a design flaw in my experience.
3) I couled be wrong, but I always download chapters wirelessly (ie. you do need to have the woreless on) That said, you can load books that are already on your hard drive with the usb. Just drag and drop.
4) If you are shopping with Amazon, then yes, I recommend you turn your wireless on. It should show up within a minute or two.
5) Books you buy from Amazon are ONLY useable on the Kindle. You can make Kindle compatible books from other sources using the Book Designer and other conversion and DeDRM'ing tools (Convert Lit is a favorite of mine for DeDRM'ing lit books from Fictionwise), and then load them with the usb cable. But not the reverse.
All in all, I love my Kindle! And I love my PRS 505! I switch back and forth with them for various reasons, and mood. I am using my PRS 505 mostly now, because I bought the light wedge and I really like that add-on.
I would buy the PRS 700 with the built in LCD front lighting, but with the economy right now, I can't justify the superfluous discretionary purchase.
As far as the technical details, I am sure others can correct me.