Hi, getvisibleuk. I have a site where I've set up a somewhat complex redirect system. The .html page contains all the text and links that it's corresponding "real" page does, but doesn't have the graphics. It does have a cookie detector, and if the user has been to one version of the site before, he has that cookie and gets redirected to that version of the site.
If he doesn't have the cookie, he gets redirected to a second page that checks connection speed ("page_a.html"). If he's on a dialup, he gets sent to to the low-speed version of the site. If he's on broadband, he gets redirected to another page that checks for flash and, if he has the plug-in, he gets sent to the high-speed version of the site.
I put a Disallow: page_a.html in my robots.txt file for all of the pages on the site.
So far, Google seems to be regarding this as acceptable. If you hear screaming in Milwaukee in a couple of weeks, though, you'll know that Google decided it wasn't ok. ;)