Rooting definitely isn't for everyone. z4Root is just fine for rooting purposes. Personally, I've rooted every phone I've had and never had a single problem related to rooting. As for OTA firmware updates, yes you have to unroot to get them, but how often do they come out and how far in advance do you know about them? It's not an issue.
The point is, rooting is a decision that each person makes on their own based on the needs and desires they have for what they want to do with the phone that they own. Personally, I want to feel like I own the phone that I bought, not like I'm just borrowing or renting it from the company that I get my service from. And yes, rooting does void your warranty, but just like the OTA, unroot it and reflash the stock firmware and back comes the warranty.
My opinion is that if someone wants a smart phone, they should have just that... a SMART phone, not some dumbed down, hobbled version of that smart phone.