StoutFiles - 4:48 pm on May 16, 2011 (gmt 0)
If you're starting from scratch, learn and use div's.
If you have a successful design already with tables, then keep them.
Div's are preferred but tables are fine; people who do web design for a living frown upon table design because it's old hat and div's have more potential. It's not worth dropping in search results because you did a full site-wide redesign that is only noticed by the people viewing your source code.