1. It is being held in Prague. If you have never been in Prague, you should not miss it! A very charming city with towers, and towers, and towers... And of course a gorgeous castle, peaceful walking streets, and a welcoming atmosphere. And the organizers secured a very stylish venue to boot!
2. Meet with people you know from drupal.org and always wanted to chat with. Morten.dk of mothership (and of course Drupalcon Copenhagen and Awesomesauce) fame, Marek, the author of RootCandy, Bojhan, one of the leaders in Drupal usability, just to name a few people. This is an event focused on design and there is plenty of space to make a name for yourself too.
3. It has a nice price! For 20 EUR, you get great sessions for two days (take a peek at the sessions already submitted), plus food and drinks at the venue.
4. Three hours of free training included! My Acquia collegue, Heather James is going to hold three hours of training with Marek Sotak on the innards of the theme system, hook_theme, and altering markup. Yes, that is still in the above mentioned price. Can you say awesome?!
5. Oh, and yours truly will be there. If that helps in your (positive) decision. I'm planning to at least talk about Drupal 7 in general, and help with the trainings.
Hope to meet you there!