This is definitely a good news because many people make spelling mistakes and it takes time to realize it and fix the errors manually. Of course, the implementation is not perfect as it relies on common misspellings.
For Google Maps, there's a custom implementation that corrects location names and addresses. Searching for [Montain Viw], you get: "did you mean: Mountain View, CA". Of course, a question mark would be a nice touch, as we're in the realm of grammar and punctuation.
* I can see this in: Google Image Search, Google News, Google Maps, Google Video, Blog Search, Book Search, Froogle, Google Groups, Patent Search, Google Catalogs, Google Directory, Google Scholar, Google Mobile Search (very few corrections), Custom Search (Co-op).