Actually table tags can be very bad.
Someone can use: (no i'm not going to demonstrate)
[/TD][/TR][/TABLE]

To close the current table, usually horribly breaking the rest of the page.
I accidentally forgot to close a table once (on my home node), and nearly couldn't get back into the editor to undo the change.

My personal suggestion is to start with the rtf format, and allow only those tags that would enable rtf-like formatting. Build from there, but slowly.