Added teh below information to existing headings.
"Is rooting easy":
UnrEVOked only works for 2.2 however. Any 2.3.3 GSM ROM must use
Revolutionary Also, any hboot 1.02 or higher needs to use revolutionary too.
Revolutionary is a joint project between Alpharev (responsible for S-off on 2.2 devices) and unrEVOked.
Revolutionary doesn't actually root the phone in itself. It S-off's the device, which then allows you to fastboot flash a custom recovery - see the adb and fastboot FAQ
here (Skip the adb section).
Once you have flashed a recovery, you can either:
1) Flash a zip to root your current ROM (if you do not plan on flashign a custom one) or
2) Jump straight to flashing a custom ROM (As root is not needed to flash a ROM, only custom recovery)
"How will I know if it has worked?"
If using Revolutionary, your Hboot version will now start with a 6.x
"Other UnrEVOked errors"
It is also worth noting that hboot 1.02 and over are not supported by Unrevoked. You may get "Waiting for root" errors with unrevoked.
"what about hboot?"
If you are on Android 2.3.3 RUU or hboot 1.02 or over, You HAVE to S-off to do what you previously could do before simply by rooting with unrEVOked.
"What about goldcards? Do I need one?"
The below statement is not necessarily true anymore. The Android 2.3.3 RUU from htcdev.com debrands (works on branded handsets without goldcards) and is still aceppted for warranty by HTC. However, this RUU doesn't work on all branded phones (theres a list somewhere of which work). In the case that your phone is not supported, see the below answer:
"
I can't boot into recovery, there is no RUU for my carrier and I don't have a gold card"
If your phone works with the 2.3.3 releas eon htcdev.com, it doesn't matter. Just use that, otherwise:
"I need to send my phone back, should I return it to Stock with an RUU?"
***Be aware, if you are S-off with an R2 hboot (example: CM7 r2), this has Write protection on it. This means that an RUU will NOT overwrite it. The hboot will remain and may effectively void warranty. It ia also worth noting that if you don't want to overwrite the hboot (remainign s-off) you must ensure that the /system size of the hboot will fit the RUU in it. CM7 is 145MB, which is much smaller than the stock 250 MB, so a sense RUU's system will NOT fit.
You need to fastboot flash the downgrade.img
If you RUU whilst on such a hboot that is too small, you will get an error stating that system [fail]. If you boot into recovery, hboot or fast boot, you will see a screen with 4x ! (1x! in each corner).
Fear not, Fastboot still works. Boto into fastboot and you will see this screen, connect usb and fastboot flash the downgrade.img then run the RUU again