Although not officially released yet, the Dell Streak 2.1 update has surfaced on Dells mobile staging servers, where many of the other
unofficially released Streak updates have surfaced.
These long-await firmware updates weren't supposed to be released until September
at least, so to have them early is an absolute god send. Whether this means an official OTA update is on the way or not we don't know, and like the previous builds we've gotten hold of, chances are there'll be little/no official word from Dell.
According to discussion at
MoDaCo, if you've flashed your Streak with a new ROM at any point you will need to revert to stock before applying the update. This update will also wipe your device, so be sure you've backed everything up before taking the plunge.
Links and everything you need to know, including download links and how to, is in
this thread. Please note, this update is only available for O2 branded Dell Streaks - from the UK, check the aforementioned thread for full details.