- Yes the price is higher, because it is unsubsidised - expect the network price to come down a lot when it officially arrives. You don't get a discount on your monthly fees though, that's the price of being an incredibly early adopter.
- You will need a Micro SIM card, but ask around the phone shops for a SIM cutter. My AT&T Go Phone SIM card is a regular size, but after chopping worked fine in the Lumia 800.
- As long as you have a SIM card, the phone will work. That's what factory unlocked means, no restrictions on which network it will connect with.
- You will pick up 3G and HSDPA where available.
Any other questions? We'll try to answer them in the comments..