I agree with you Pete... and I have not tried this either since I've been rooted forever!!!
But also, since I've been looking in on the Galaxy Nexus and might get one in the next couple weeks... they not only unlock the bootloader, but then have to still perform a root process to allow them to load Superuser and Recovery... so unlocking the bootloader might not be the only thing you will need to do.
Exactly. Usually when people refer to "rooting" a device, there are actually 3 major steps involved:
1. Unlock the bootloader. This is more for "behind the scenes" kind of stuff, but is a very important step. A
fully unlocked bootloader will let you flash radios and un-signed updates (which, by the way, I've read the HTC official unlock process will NOT let you do), but more importantly allows you to...
2. Flash a custom recovery. Think of the Recovery partition as a pre-install environment, kind of like a bridge between the BIOS and the OS itself. For those familiar with installing Windows on a computer, the Recovery environment is similar to the staging environment that you boot to from a Windows install disk. You basically have a minimal interface where you can mount and format disks, as well as install the operating system from outside of the live running Windows environment. The custom Recovery is what allows you to flash ROMs.
3. Root access. In the Linux world, "root" = "administrator" on a Windows computer. By default, most of your apps on Android run under the general user account, but just like in Windows, if you need to modify system files, you need elevated privileges for this. Granted, this is both a security measure, as well as a measure to keep idiots from complete jacking-up their devices! Once the OS has been "rooted", you can then grant root permissions that apps and/or processes that require it though the Superuser app. Pretty much every ROM out there has root access and Superuser app pre-installed.
Long story short, the official HTC unlock method only unlocks the bootloader, so you still would have to flash a recovery and gain root of your current OS if needed.
I can almost guarantee you a full method write up on just how to do this will be available very shortly...I'm just certainly not about to do this on my already rooted Thunderbolt.