Tell HN: Upgrading to Rails 3 is a side project, not a todo item
I've spent about a week now upgrading SproutRobot. The changes aren't that substantial, but there are lots of little differences. I've spent a lot of time tracking down silly little bugs in my code. Granted I'm also migrating from Webrat to Capybara, but getting Webrat up and running was turning out to be a project in and of itself.
YMMV, but my recommendation is to make a rails3 branch, spend a day on it, and then get back to real work. Spend a day a week on it until it's done, but don't expect that you'll be able to power through.