I have worked with a lot of different MultiSite setups - some better than others. Nonetheless I'm not using it anymore - but I still think it's relevant - as Mike mentioned, managing 450 sub-sites separately would be impossible, and that's when it's good to use MultiSite.

The country I live in, developers tend to use multisite as an alternative to a language-plugin. In my opinion, that's not the correct use of this feature.

I'm glad it's not going anywhere though! :)