Recently, we started to develop Vaadin 6.8. How complicated will it be to switch to Vaadin 7 after the initial launch?
Check the Wiki to see how things will work in Vaadin 7 and judge for yourself how deeply you will be affected …
If you haven’t done any custom client side code, then it should be quite easy. The main changes are that you should use a Root instead of Application and Window. You can also use LegacyApplication or something like that to get into business straight away. Most of the other changes have the old way there but deprecated - so they should work. With custom client side code you might be in for a bit more work but there are legacy classes there as well that can be used.
My tip is that you drop in the new vaadin jar and see how much errors it’ll show. My guess is that you do fix it into a working state somewhere between two hours and three days, depending on the project. After you have it fixed, you can start taking use of the new features mentioned in the link that Tobias posted.
Thanks for the answers!