Best Buy has been slowly developing a retail relationship with Apple. A few years ago, certain locations were given Mac minis to sell. That program has matured to the "mini stores" in place today. AppleInsider suggests that a major overhaul of the mobile phone departments at all Best Buy locations was the step that finally convinced Apple to hand over the iPhone.
So, will Best Buy move many iPhones? I still encounter much anti-Apple sentiment from hardcore Windows lovers, and big electronics stores can be an epicenter for that type of thing. However, it seems to be reserved to Apple's computers.
My hope is that the staff is well trained, as I'm sure we all remember the unpleasant experience of shopping for Macs at Circuit City several years ago.