Anyway, it supports both Entity Relationship Diagrams and Data Flow Diagrams. Which is actually jolly exciting: I can't remember the last time I drew a DFD but it was probably in 1999, the last time I worked under SSADM. As a possible replacement for Oracle Designer I think the biggest drawback is that it doesn't separate the logical and physical models: they're just two views we can toggle between. I don't know how many people actually maintain two separate models these days, but I would guess that the sort of people who care about data modeling are likely to be the sort of people who would want to keep the logical and physical models separate. And the rest of us will continue using Schemester or some other freeware. (There is going to be a freeware verson of TDM but it won't have all the features enabled; most notably it will lack reverse engineering).
Interpretation: TOAD stays one hop ahead of SQL Developer. Or two if you're one of those people hung up on the performance of your tools.
I suppose I ought to make it clear that I haven't actually used TDM. I have had bad experiences when using a crippleware version of TOAD IDE. But maybe I will download the evaluation copy and see whether it cuts the mustard or cuts the cheese.