I haven't read much about how carriers feel about this.
For example: Will it be the end of tethering fees? Because root privileges on an HTC EVO allow you to tether wirelessly, circumventing an addition $30/mo, will Sprint just stop charging for tethering? Or will there be another level of restrictions in place to prevent it?
Here's hoping there's an unlock for Desire HD, nobody has managed to root the latest version yet, which means that you can't root it without erasing all your data and downgrading...