yep, I know what it says, but (without saying that they are wrong) there are much more things to consider in practice....
It's hard to explain in English for me... I once (not so long ago) found an excellent page which backup up my points that I wanted to came across, but sadly, lost the link....
sidenote: Image are of course in pixels, and that proofs that the fact that HT(ext)ML in in fact not meant to create graphical content where everything hangs together and is absolutely dependend on other objectsizes. Of course it depends on who your usergroup is and what they use to view the "web"... if you have a very heavy graphical content and you use text that absolutly must fit into this graphics then it's indeed usefull to use px, but in all other cases it is better to not use it at all.... You should always take in account (or try to) that a user will not have the same DPI, windows fontsize and browser then you use. Because all that makes how the users sees the page. Also for people with vision problems who use special tools to view pages, bad use of px can be realy annoying because px sizes are very very small on large DPI screens, while pt-sizes or em-sizes (I could be wrong there) are not....
EDIT: something to back me up a bit:
http://www.web-graphics.com/mtarchive/001165.php
(not the site I meant above, and not the best explaination, but similar, oh well...)
/ 
