I have 650 and I'm very happy. The extra $ was worth it. But if I broke it tomorrow, I might get a Nook because of price. It seems very nice.
Maybe you could cross the border to pick one up? How does that work? Apparently you need a US address or something. I imagine you can get round it if you know what you're doing.
What's more it has a nice looking browser. On a downside it only supports epub and pdf, and it's pdf support is primitive.
Re: the Kobo, it looks nice too, but one button? And no annotations?
Re: the 350, I'm sure it's very nice but I wanted that extra inch
You should go for it or not? If your 505 is working, wait a bit. But the 650 is almost perfect if you don't care about wireless.