Spartacus,
To be honest with you, CSS (cascading style sheets) have been around for quite some time now, but they are becoming more popular now that al major browsers support CSS, There is nothing magical about using CSS.
CSS is just a tool that allows you to sepate the look of your web site, from the content (allowing for search engines to crawl through pure content rather than Images slices and so forth.
I wouldn't say that CSS is user friendly (there is a learning curve and not knowing how to edit such files can collapse your web site (if it's table-less based design)). I think what you meant to say was that it is cross-browser friendly, with the exception of Internet Explorer 7.0 and now 8.0 beta.
The truth is that all other browsers such as Mozilla, Opera, Safari and Chrome are on the same page, except for Internet Explorer, they don't care to go along with the rest of the world, this makes a developers work much more harder, because now you have to include IE Hacks (which I don't care to do) but it's just the extra leg work.
Web Sites in CSS should not make your price go up or down, it is up to the developer and what he feels comfortable with. Although, I do argue that for accessibility purpose once should go with a full CSS table-less web site, especially if you want to be able to see it in IPHONE or PDA.
As far as Search Engines are concerned, YES, having a W3C.org validated web site does increase your search engine ranking, because it has less structure to parse through. Table based layouts are more bulky and tables should only be used only if you're going to display tabular data i.e. Products.
From what I've been reading you are looking into incorporating a flash gallery? If that is your intension, make sure that it is soley to to display your pictures... but not as your primary tool to have your site developed. It will decrease your chances of indexing in the search engines. Although, Flash looks good, it can cause some serious damage if you are planning to compete in the Search Engines and against Competitors.... To have a better understanding of what a Table-less web site is, check this site out;
http://www.wsrealtyinc.com this web site is completely in CSS no tables other than the rent to own page, just because it's tabular data... (coming from the database)
The only disadvantage that a CSS layout faces is: Depending on the end user's habits and how often they upgrade their machine is now your web site is going to render, for example if a customer is still using Internet Explorer 4.0, 5.0, or 6.0, PNG images with transaparent do not render correctly (they Look Gray-ish) and if you have a very colorful template guess what? its not going to look very colorful. There is also another issue with older IE Browsers and that is the 3-pixel jog, forcing developers to float div tags. (div tags is another aspect of CSS and table-less designs)
The advantage is: Well, everyone with an updated machine is going to appreciate your web site, search engines are going to feed off of your content much easier ** Depending if the CSS was coded correctly, aswell **.
Another advantage of having a CSS based web site is that, you can change the layout of your web site much faster than using tables.
If you are looking into having something that you can update yourself, meaning the images and verbiage I'd advise you to go with a Content Management System Such as Joomla or Word-Press (though they require that you learn how to use them) it might be your best solution. By using any of these content management systems, search engines will index your content faster for the simple reason that Search Engines love Fresh Content and if you are always updating your site, you are indexing faster because of the "time stamps" so you would have something like: last modified on: "The date", not only that, but a Content Management system allows you to Syndicate your feeds (RSS or ATOM) making your content much more richer and allowing others to feed off your site via XML (RSS) as well.
Finally, it allows you to multiple templates installed, and swap back and forth if that's what you intend to do.
I hope I've explained myself and that you gain knowledge and a brief understanding of what CSS is. I am actually writing an E-Book on "How to Choose the correct Web Designer for your project" Most of the stuff I talked on this thread can be found on the public domains, but what I wrote is based on my experince and knowledge.
I noticed that you are a photographer? Email me, I have a web site to share with you.
Your web site will only be limited to your designer / developers experince and knowledge.
