This might be already old news for you, but I just discovered that my Google Drive had been upgraded to 15GB instead of the usual 5GB.I even have an account where I got 1 additional gigabyte for being an early user. That's pretty cool. The other thing that changes is that now the disk space is unified across Gmail, Google Drive and Picasa. This means that if you used your Gmail to save or send files like pictures (not really the best use for Gmail but many people do that), you might actually find yourself with much less free space, depending on your usage pattern.
For most users, though, it is probably a nice (and welcome) bonus.