I am a wordpress loyalist and so I would say without any hesitation: use wordpress. Here are the reasons why I favor wordpress (some of which you have already mentioned):
It is free, so you do not have to buy any site-building software to make your website (those software are mostly expensive!!!)
It is easy to learn and it is continually updated and improved upon by many experts worldwide.
It gives you a wide choice of themes to use so you can be sure to find one that suits your taste and needs, and many of those themes are free
There is a huge number of plugins available to add functions and capabilities to your wordpress site. And more plugins are being developed all the time.
You mentioned "websites that specialise in building these 'sales letter' style sites, they all seem to be building it using xhtml and css" and I presume that those are sites that build your website for you for a fee, and of course they would custom-build sites, that is why they use those.
Wordpress also uses css stylesheets - such are included with the theme files.
Wordpress or HTML?
Linear Mode
