XHTML CSSp is it ready for the Prime time?

Hi all
simple question really, Im about to rebuild a site for a client and Id like it to be the bee's knees of accessability. I'd love to make it xhtml compliant with a nice textual version for the screen readers etc. however this will require CSSpositioning as tables are not allowed for layout in strict XHTML.
Do people think CSSp is OK cross browsers, are there any good detection scripts for browser support (rather than detecting browser type) how bad will NS4 make it all look?
whats the general feeling, Id like to make it accessable but not at the cost of the end users, some of whom will be on old browsers...

Actually tables was never intended to be used to controll the layout.

from the html 4.01 spec


you can take a look at ie. wired.com
they are using css to do the layout,
and they serve a plain text version to useragents that isn't compliant.

Cheers for the link, not a bad job they've done at wired.

anyone know of a method for detecting if the browser can use cssp I don't want to do a browser detect just a capability detect.

Ive been doing a bit of testing for browser compatability.
whilst looking into this I found
http://www.skyzyx.com/archives/000094.php
this is a smart way to run multiple versions of IE on 1 machine so you can see all the bugs your end users will.

I must say that this puts me off using CSSp on this job. a lot of my users will be using Ie4 and looking at wired with it brings up a load of bugs (although IE4 is supposed to cssp)
I know xhtml and cssp are the right thing to do but I cant easily justify it to the client when tables can do the job.

I realise that tables arent designed for layout, but people want layout so I've got to use something...