Gmail upgraded the maximum attachment size from 10 MB to 20 MB. Gmail was quite forgiving and you could send more than 10 MB in some cases, but now it's possible to send at least 20 MB in one message. Of course, few mail providers will accept a such a big message, so it's safe to send messages bigger than 10 MB to other Gmail accounts, to Yahoo Mail Plus or to other premium accounts. It would be nice if Gmail showed a progress bar for the upload and if uploading files to Gmail was faster and more reliable. But maybe we're asking too much :-)

However, I would imagine that this will significantly cut down on overhead (and improve efficiency of) GMail storage-related applications such as GMailFS or GMail Drive. GMailFS uses a virtual filesystem, so doesn't have file size limits, but GMail Drive is strictly one-file-one-attachment (a significantly less efficient method), so at the very least it doubles the max file size you can store with GMail Drive. None of the current GMail filesystem applications seem to be ideal implementations though (GMailFS's creator admits that using subjects for metadata was a bad idea, and GMailDrive's approach is severely limiting), so the possibility of significant improvement in such third-party utilities is quite exciting!