How does the Blackberry warranty work?
Will they replace my phone with a new or a refurbished phone?
Do I have to pay when I send my phone to them?
EDIT: Also, is this Blackberry 1-year warranty only if you bought it from RIM? What if you got yours from AT&T?
Like Candy84 said, Days 1-30 are a new device (usually provided to you by AT&T), days 30-335 are covered by RIM, in which you'll be issued (usually) a refurb device, however refurbs are far better than they used to be in general.
This is how the policy works if you purchase the device from AT&T (or most any carrier) since it's not possible to purchase a device directly from RIM, Do note that you may also have some extra coverage on your device if you signed up for AT&T's EQP package which entitles you to a new device beyond the first year for a deductible of 135.00.