Forgetting about things that pertain exclusively to the developer like code maintainability and religion wars about semantics and what-not, my question is: what real world problems does using tables present to the user? Are there device that cannot understand a tabled layout properly? Does it decrease the page’s relevance on search engines?
Of course I’m talking about a reasonable layout where tables are only used for things that in pure CSS/divs require hacks (and for tabular data obviously) — not things like a hundred nested tables maybe even used instead of ul/li.
Tables are such old technology that they are reliably rendered on every device and in every program I know.
I am not encouraging the use of tables for layout unless really, really necessary (which it is in a few cases), but I do not believe a well done layout using tables for some aspects does automatically affect rendering negatively. Feel free to prove me wrong, though.
There may be problems for text to speech programs when a table is used instead of the semantically correct element, e.g. in ordered/unordered lists. But I believe that any text to speech or other accessibility software has provisions for this, otherwise it would not be usable on today’s Internet.
There may also be cases in which a browser that needs to intelligently resize a web page (e.g. a mobile browser) has more trouble with tables than with other layout elements. But that depends very much on the individual layout and situation.