Actually when you get to building CSS layouts its easier / quicker / more efficent to make multiple skins with just a small amount of code changes. For example A similar skin but with the main content pane split into 2 smaller sub panes.
<div id="wrap">
<div id="ControlPanel" runat="server"></div>
<div id="tagline" class="tagline" runat="server"></div>
<div id="loginlinks">[USER] [LOGIN]</div>
<div id="logobanner">
<div id="logo">[LOGO]</div>
<div id="banner" class="banner" runat="server"></div>
</div>
<div id="imagenavbar" class="imagenavbar" runat="server"></div>
<div id="content">
<div id="contentpane" runat="server"></div>
<div id="contentpaneleftside" class="contentpaneleftsidewide" runat="server"></div>
<div id="contentpanerightside" class="contentpanerightsidenarrow" runat="server"></div>
</div>
<div id="sidebar">
<div id="MainNavBar">[HOUSEMENU]</div>
<div id="leftpane" runat="server"></div>
</div>
<div id="date">[CURRENTDATE]</div>
<div id="footer">[COPYRIGHT]<br />
As you can see it took 2 small short line of code to take my main contentpane and split it into 2 smaller ones. Doing it with a table adds a bunch more code as your spliting a table column or creating a sub table for 2 more cells nested in one table cell.
The reason why CSS are the new hot fab of the web, is based on a recent push by many governments, states, and countries to mandate compliance to accessibilty of the net.
Tables are not screen reader friendly, they don't scale well in different monitors, and were never suppost to be used for layouts to begin with. They are sort of a bad hack gone way to far. Not to mention they bloat webpages, are less resource efficent, and prevent caching options. For example my CSS skins load about 4 times as fast as a few table based ones I have yet to convert. The reason is I can cache the CSS file on the server, so all the browser is processing is the html which is about 10 lines long.
I have created a 23 pane layout for a customer in 60 lines of html using CSS layout. While doing the same layout in tables was around 200 lines of html. I converted their site for them. Ended up being a saving of about 1mb in file size, doesnt seem like much but the site had 2k visitors a day. Saved them around 2Gig in bandwidth a day.
So there are times when you can really see some huge gains from CSS layout. The problem with CSS layouts is most people have a bit of trouble in thinking of them like a table, but just with different tags. Once you start to compare a CSS layout to a table layout there are tons of similarities in overall method. People just not use ot it, yet. I say in 2 or so years table layouts will be a thing of the past.
HouseMenu is pretty easy to use. They just launched a new beta for HouseMenu version 2 which really adds to its capabilities. Can read up on it a bit at houseofnuke.com
If your interested in CSS styling and want to get a serious leg up on skinning DNN with CSS and housemenu, www.dnncreative.com is a good source of information. I found the subscription worth every penny, myself, and cant remember anyone complaining about the site / content. Lee does a good job with his tutorials.
There are also some free CSS based skins to look at / reverse engineer / learn from, and a section dedicated to CSS skins.
Hope all that helps you. Let me know if you ever need help with something. I am working / building a CSS layout skin library. Kinda hoping to get DNN 5.0 soon though cause it will make installing / using all my skins simple for everyone.