However, it's likely we'll see specialized adapters and hubs that preserve the Thunderbolt chain while branching off to provide USB, FireWire, Ethernet, video, or audio connections. These could range from simple, T-shaped adapters that provide Thunderbolt input and output along with a single legacy connection, to multi-device hubs that let you connect several legacy devices (docking station, anyone?). When using one of these specialized adapters, the higher performance of the rest of the Thunderbolt chain should be preserved.

Until such adapters are available, one of the biggest Thunderbolt challenges will be that your display must be the last device in the chain, because the new MacBooks have only a single Thunderbolt port and current displays--even those with DisplayPort connections--don't have a way to pass data on to another device. This will make it a hassle if you want to temporarily connect or disconnect, say, a Thunderbolt hard drive, as you'll need to disconnect your display in the process.

We suspect that, with the exception of displays, most people will choose to connect their existing peripherals to their computer's USB, FireWire, Ethernet, and audio ports.

We suspect so, but we haven't yet confirmed this capability. We'll update this answer when we know more. We're also looking into whether you can boot your Mac from a USB or FireWire drive connected to a Thunderbolt port using an adapter.