DIVs do not always work properly and there are many differences between browsers (mainly older ones) which will change the way a page will render when made entirely from DIVs. Tables can often overcome these issues and are generally more stable and predictable across a range of browsers and platforms - not least of all with compact browsers such as those found on smartphones/tablets. Often these employ compression and layout alterations which can drastically alter DIV rendering.
Tables are very compatible and have been for a long time. For the very slight overhead in processing power they require to render as opposed to a DIV based layout, I see no reason not to choose them over DIVs if they work better for a given application. Just because something is not "best practise" on paper, doesn't mean that is so in the real world!
I like the site design, I think it is clean, uncluttered and straight to the point. Good luck with it!