a couple of weeks ago i added myself to the waiting list (well, it was there) for the new version of Yahoo! Mail, and two days ago i got it. well, the realm of web applications never looked so close. it acts very much like a desktop app, with even the typical windows beige color (i wonder how does it look on other systems?) and all. on the left pane you have a list of folders and RSS feeds, and contacts link that opens in the main pane. the calendar and notpad are there too, but they open a new window with the old version of these utilities. the RSS feeds are what you have in My Yahoo, if you use it. i didn't check if they are synched, because i don't use My Yahoo anymore.
of course, there is rich text editing (but no text direction yet, for those of you not writing from left to right, like hebrew or arabic), you can open messages in new tabs or in new windows (this might cause trouble to IE users, because it's popup blocker sux), and it has context menues on a mouse right-click. i had my mozilla set to prevent sites from disabling my context menu, so the mozilla context menu covered the mail context menu, until i let it hide the mozilla menu.
multiple encodings are supported, including hebrew (windows-1255, and some old IBM encodings, but not visual hebrew), and you can switch encodings from a drop-down menu, which is very usefull if you communicate in more than one language, like me.
you can also search the mail, like before, and the options link will take you to the old options page.
oh, the ad is a "tower banner" at the right of the screen.
i think it's about time we start have links to web apps like this one from our desktop, instead of opening a web browser for it.