It's awesome to see that Laszlo has gone open source. The main reason I haven't dug into Macromedia's Flex is because it's $12K per CPU. I agree that this it's probably worth it if you're after a nice user experience - but most of my clients want open source, and only open source. It's tough to find folks that'll pay for JIRA even - if you can believe that.
With Lazlo going open source, it opens a whole new world for me. Now there's an opportunity to use this technology with clients. Of course, now I have learn the stuff so I can be productive enough to convince them to use it. I may even add a Lazlo front-end to AppFuse, but probably not until next year, after Tapestry and JSF. Hmmm, if JSF is really all that - can it render a Laszlo UI? That'd be wicked.