The "Buy Root Friendly" list: Android devices ordered by ease of root
unrevoked.com
unrevoked.com
http://www.cyanogenmod.com/devices
But new devices are being added every week, like the Motorola Defy was accomplished yesterday.
(in a nutshell cybergenmod is a clean, easy way to put the far newer and feature-rich 2.3.3 on those devices)
The note "Important: phones may change from one category to another when manufacturers and carriers release updates." refers to obtaining root access on a new phone.
1. regardless of whether you install a custom boot rom, the lowest-level software running on the phone might be impossible to overwrite, so the carriers still have some basic low-level access to your phone to tell android to lock you out.
2. any such feature is part of the code that is itself replaced when you install a custom rom, so would be defeated and you'd be safe (at least as long as the model you buy does not turn out to have become locked down during the manufacturing batch you end up buying).
It sounds like 1 is just not the case, thankfully.
Motorola has apparently rolled out silent updates that kill root. This is why they are in the "poor" category.
http://www.androidpolice.com/2011/04/12/happening-now-droid-...
What a great contribution. I hear there's some new snide remarks on Daring Fireball you can copy/paste here.