Just been testing Designer 2. Brilliant ideas! You guys were probably high on the past few months!

One minor bug:
in the code editor, when typing new lines, the cursor seems to run away from the code after a few characters. eg add a tool click event and in the code of the event, try typing in: alert('hello world');
After typing the l the cursor is one character further to the right than where you are typing. By the time you get to the first ' it is about 5 characters to the right of the text, making editing code very, uhm, difficult, tricky, challenging, lets settle on fun, but with limited patience

One major bug:
Create a new 4.0 project. Add a viewport containing a panel containing a label. Leave everything as default. Saving and exporting results in nothing being displayed and nothing picked up by firebug. The project defaults to 4.0.2a, but the same results seem to happen for 4.0.7. Not sure if its related, but no designer_includeOrder.txt gets deployed and creating it manually does not resolve the issue.