I have rooted my phone using z4. I am running the pick N pack 3 rom.
It was not terrible difficult to do if you have done other phones in the past.
Rooting your phone does not wipe out any software or change out your rom image. It strictly allows applications to execute with higher privileges.
It will let you run things like "Wireless Tether for root user" . You will however need those elevated privileged to be able to replace the rom image on your phone.
I updated my phone to 2.2 so i can use Google Voice Actions. I have had it on many of my phones in the past and missed it. After upgrading my phone, the Google voice actions has a bug. I am unable to call or send text using voice actions. It seems voice actions will not see the last name in my contacts. I can not tell if this is an error with my Google account or on my phone.
I got my rom Image from here http://forum.xda-developers.com/showthread.php?t=970331
but it seems it has been taken down since then.
I do hear that Cellular South is coming out with the 2.2 update. They have been telling me "in a few weeks" since mid Feb. It is getting VERY frustrating. I asked them again yesterday and now they are saying the end of April. Anyway, I hope this helps guys.