Evernote announced a shiny new web interface. It is still a work in progress and missing a few features, but it is more like the Windows client then the old web interface was.
Why would you use the web interface? Maybe you are at the library or somewhere else you are working on some one else's computer.
The big reason I think Evernote is putting the effort here is so Evernote will have a good presence on the Chrome OS. Sixty thousand laptop were given away with Chrome OS on it, and the reviews seem good. This summer, inexpensive laptops (I hear like $200) will be coming out with Chrome OS.
I think a lot of non-geek users will love Chrome OS. No antivirus programs needed. Lots of good, free software (like Evernote and Google Docs). And very little self maintenance needed to maintain the environment. I think it could be a big winner for family users.