Over the last couple of days, the team at Laszlo released LaszloMail (product link) to the public, showing us what a Flash based UI really can do. So I got my testing account, logged on and had a play.
It provides what you would expect from a typical 3-pane mail application -- folders on the side, message list at the top and the message preview down the bottom. User interface-wise, it is impressive. It is impressive comparing to other port 80 applications, in terms of providing desktop application-like look 'n' feel and responsiveness. It makes no attempt to massage HTML into doing what it was not designed to do, i.e. drawing widgets that looks like desktop counter-parts, providing dynamic feedbacks, changing behaviour after an asynchronised reply received from the server, etc. It leaves all that to Flash, doing what it is best at, i.e. user interactivity.
Comparing to Ajax and DHTML, it is revolution, not just evolution.
Functionality wise, I don't think LaszloMail has provided anything extra ordinary. You can send, receive, create folders, spell check -- just like most other web mails, yet it lacks some innovative features of other offerings, especially those of Gmail.
There are other issues associating with Flash-based RIA. Uploading attachments still require popping up a new window -- it is simply not possible to handle file upload right inside Flash. Memory usage is also a concern. Firefox's memory usage goes all the way from 20Mb to 80Mb just to load the 3-pane interface. That would be a show stopper for those average household who upgrade their computers every 5 years -- they won't be able to run LaszloMail without constant swapping.
But at the end, I don't see LaszloMail as a competitor to Gmail or the up-coming Yahoo Mail/Hotmail upgrades. It is more like a technology show-case, helping us to glimpse what a real RIA would look like when the right technology is used.