Pretty amusing... GOBI, thanks for the redundancy! (???) Posting the link again from the OP. Hmmmm. Anyway...
Fenga... can't brick it, unless you do something extraordinarily stupid like pull the battery as it's writing to the system folder, lol... Not that this is impossible, just
highly improbable!
Lozer and Hero... This is NOT a ROM replacement that you will load onto your phone. It is a process which will grant you ROOT ACCESS to your phone. Just like getting to the ROOT folder on your PC.
It "IS"
still the OFFICIAL SPRINT UPDATE residing on your phone after ROOTING.
You can leave that there and not replace it, or if you chose, then you could load a different ROM onto the phone if that is what you want. I have the stock Sprint release on my phone and nothing more than ROOT and recovery which is nice, because at the very least, I have control over which apps are on my phone. Gone is the Sprint Bloatware Junk app's taking up space and cramming my phone with un-needed, unwanted, unasked for app's. Spint TV, Amazon MP3's, etc...
How to remove Stocks, Nascar and other useless apps... - xda-developers
READ through it all... but it is very easy.
The recovery NANDROID Backup option is wonderful, it actually makes a backup of you phone in totality, EVERYTHING as it is... in the event that you wish to put it back to the state it is in, phone numbers, settings, scene's apps, etc. all go back to exactly as it was when you used the Nanadroid Backup.
At the very least, those are two reasons I ROOTED. Lastly, the Hero will shortly be reaching EOL with all the newer, faster and better locked phones coming out, there is no better way to find some support in keeping it (Hero) going just a little while longer than by using one of the ROM's from the Dev's over at XDA. Something you won't find at Sprint or HTC.
All just my humble opinions, ultimately, the decision to ROOT is yours.
HappyTrails!