If you don't know, super CID is more or less like root for hboot/fastboot. Why do we care? It means we can install any ROM we want if the propaganda is to believed.
More importantly, it means we don't have to lock our bootloaders before we RUU if we don't want to.
Here are the simple steps to get super CID.
S-OFF is required.
1. fastboot oem readcid
2. write down your existing cid.
3. fastboot oem writecid 11111111
4. fastboot owm readcid
5. verify it has changed. It should list your old CID as your backup CID.
I tested this by flashing the 2.x RUU, unlocking the bootloader via HTCDev, and then flashing the RUU again immediately after I got unlocked.
--As is noted by other people. This isn't actually useful for us. But yay, now you know and don't have to spend 5 hours researching like I did.