Do NOT use a one click root. One clicks lead to bricks. They are bad news. I would recommend using the adb manual root. It's copy and pasting. Pretty simple. Just find the ADB for dummies guide then the manual root guide at XDA.
All functional ROMs for the time being are based on 2.2. We will probably get a gingerbread leak within 2 months. If not 1.
You can't really "backup" your data before you root. Rooting wipes EVERYTHING on your phone. Once you are rooted, you can get Titanium Backup and you will be able to make a backup of all your apps and system data.
Sent from my BAMFed out Thunderbolt
There aren't any one click rooting solutions for the Thunderbolt right now. There are many tutorials on how to root the TBolt. It seems pretty easy, but it does wipe your phone (the main reason I've been holding out on doing it)
NOTE: Z4ROOT WILL NOT WORK ON THE THUNDERBOLT. The other poster had a Droid X, which I believe does work, but it DOES NOT WORK ON OUR PHONE.
I disagree with "one clicks lead to bricks". You can brick your phone using ANY rooting method. Every rooting method I've seen has a CYA disclaimer that you can damage your phone and they are not held liable. Many people have successfully rooted their phones using apps like Z4Root, Unrevoked, etc. The dev community wouldn't create one clicks if there wasn't value or the software didn't work. There is obvious community bias against people using these solutions without knowing what they are getting themselves into, or what rooting their phone actually is.
The best advice is to learn as much as you can about rooting, learn about ADB, and make your decision from there. Just be aware that rooting the TBOLT will WIPE YOUR PHONE.
Good luck.