pgAdmin III bundled tool is 1.4 - I think I was using 1.3 last time I installed. Visually it looks a bit nicer - I'm assuming they've fixed some bugs or something similar to warrant a number change. :)

1.3 was the development series for 1.4, the new stable release as of yesterday. There are a heap of new features over 1.2 (which shipped with PostgreSQL 8.0) - see http://www.postgresql.org/about/news.419 for details.