The new site makes available more of Microsoft's linguistic resources than ever before.
Using the Language Portal interface, one can search Microsoft terminology and UI strings from most released products: Language Excellence has thus made available the MS Glossaries, once hidden under MSDN.
The portal offers a page for sending terminology feedback back to Microsoft, a link for downloading Microsoft's Style Guides, a "Language Portal Blog", articles, links to events and to other linguistic resources.
In the search interface one can look up a word or string and search its translation in any of the dozens of languages in which Microsoft products are translated (of course, the coverage for some of the languages will be more extensive than for others).
The search may be run on all the products available, or restricted to a specific piece of software.
The results page is divided between a Terminology pane, which provides Source, Target, Definition and Product, and a "Software strings" pane, with Source, Target and Product.
Searching through this interface will probably not be as quick as searching on the Microsoft's glossaries stored locally on your computer hard disk; on the other hand, the results obtained should be more up to date, and searching for translations in several different languages will no longer require downloading several gigabytes of zipped files on the off-chance that they may come handy one day.