It all depends on the scale of the site.
FYI:
http://stevesouders.com/efws/css-selectors/csscreate.php
*Pretty Neat
Most are not so fanatic lol
:vinnie: (= high five) lol
That’s what i stated in my earlier reply:
Performance problems would only likely to be on large sites because the selector would have to go over every element, but it can happen.
I don’t think that there are actual figures to back that statement up:
Wanted to give you some actual figures 
I still start off with
- {margin: 0;}
but thats because it saves ME a lot of time… all those margin: 0’s I don’t need to write for everything else : )
And tnx for that … interesting links
Nothing wrong with that: like a lot of things there are several ways to do something in CSS.
Off Topic:
Yes I bought the Steve Souders book and it’s an interesting read. As mentioned IE performs fairly ok until it hits a wall and then it slows right down. On most small sites the differences would not really be noticeable but on large sites performance can be increased by following his rules.
However as pointed out by others there are more important considerations that should be done first and will give greater benefits. Some people are cutting theirs css down to a minimum of 20k yet their logo is about 250k and they could have optimised it by 20 times without loss of noticeable quality.
I liked the part in the book about how bad IE expressions were for performance and utilised his run once expression in my demo.