As someone who just implemented automatic table layout and is now intimately familiar with the details of how it works, I'd like to suggest that the problem with table-based layout is that it's excessively complex and largely undocumented and unspecified. The results will differ between browsers. Even the parts that have draft specs (which don't include, for example, percentage heights) are much more complex than CSS blocks and inlines: look at sections 4.1 through 4.4 of [1] for example.