Windows Live Mail Desktop, currently in beta, is a replacement for Outlook Express, although you won't find it in Vista. The program looks so similar to the Live Mail site that it's hard to notice you're actually using a software. This is probably the first program built from the interface of a web application.
The first thing that strikes you after installing the program is that you have to sign in with your Windows Live (MSN) account. You can ad more accounts later (and even your Gmail account, that is just a regular POP3 account).
WLMD has a 3-columns interface: the navigation, mails and contextual web results and ads. If you click on a mail, the programs scans the text of the mail, finds the most relevant keywords and shows the first web results for each one of them along with some ads from Microsoft adCenter.
The program has a feed reader, but it doesn't work unless you have Internet Explorer 7. That means it just reads the feeds from IE7.
I imported all mails from Gmail to test the speed of WLMD and I must say it's fast. But fast doesn't necessarily mean smart. The program sent a lot of random mail to the Junk folder, mostly short mails.
The attachments are very easy to miss. The icon is very far away from the mail and should have been replaced with the name of the files.
The search function works fast, but it doesn't highlight the results in the mail body.
You can compose more mails at once, attach files using drag-and-drop, forward more than one mail, insert photos directly into the message.
You don't have advanced options like "see the raw mail", filters are created as non-intuitive as in Outlook Express, while contacts are added through Live Messenger.
While WLMD is an improvement to Outlook Express, it lacks a powerful spam filter, a contact management feature, mail threading and a real desktop look-and-feel. Plus it needs a lot of RAM (on average, 70 MB, which is too much for a mail client).
Here's the direct link for Live Mail Desktop (13.5 MB).
More Windows Live:
Live Messenger review
Live Mail review
Live Toolbar is impressive