I like this kind of announcements and alliances. Makes me feel that openness and the right things can be successful.
The Android (formerly GPhone) platform (or parts of it) will compete with Windows Mobile, Symbian, S60, QTopia and other Open Source initiatives as Open Moko.
For developers there is nothing to download yet (expected for November 12).
Currently there is no single mobile platform that makes me truly happy. Symbian+S60 is the most advanced but still very proprietary. Windows Mobile seems to have a great future, and all Open Source initiatives are currently mediocre. Access (former Palm Source) is also going towards Linux but still feels proprietary.
If Android takes off — I mean, in a mature way — we will have the chance to use mobile devices as our computers: installing whatever OS we want.
I wish to welcome the OHA initiative and hope they can learn from the problems and mistakes of the GNU/Linux community to avoid them: ecosystem fragmentation because of too much platform packaging (a.k.a. too many distributions), overall lack of project management with architectural vision, too much religion, lack of true integration between different software components (because there is no real cross architectural vision), and lack of true support from proprietary hardware components manufacturers (a.k.a. lack of descent device drivers).
From the list of alliance members I miss names like Nokia, Red Hat (as a big Java player) and IBM. But I believe this is question of time.