Chris notes that the new toolbar comes with query suggestions, similar to the version on Google Firefox toolbars:
The new query suggestion feature is similar to the "auto suggest" feature that's currently available in the Google toolbar for Firefox, with a few new twists. In addition to suggesting popular queries that match the words you're typing in the search box, the new feature also suggests spelling corrections and also presents potential options from your own toolbar search history and bookmarks.
The features work across different computers, so if you search for something on one computer Google lets you access that on another computer. Perhaps this is why Google has been so slow with marketing something like Del.icio.us?
It looks like they are trying to kill off the misspelled keyword market, but I am not sure of what I think of the new spell suggest feature, especially when combined with search suggest.
Lets say young Timmy, a second grader, is trying to use Google to remember how to spell Jenna. Google rewards his correct spelling by suggesting that he view a couple pornstar websites (as the top couple most frequently searched for Jenna results are pornstar names).
Google also opened up the toolbar with this release, allowing third parties to create custom buttons. The API looks pretty simple. New buttons can act as a custom RSS reader, and it is easy to submit your button, although the TOS prohibit gambling and certain other sites. Some of the early listed sites on Google's button pages surprise me.
The new toolbar is an IE only US only release.