It's still not 1.0 but it's shaping up nicely and is already widely used. Consider the API to slightly improve over time but we don't plan on breaking it.
Jinja 2.4 and Werkzeug 0.7 or later. pip or easy_install will install them for you if you do pip install Flask. I encourage you to use a virtualenv. Check the docs for complete installation and usage instructions.
Go to http://flask.pocoo.org/docs/ for a prebuilt version of the current documentation. Otherwise build them yourself from the sphinx sources in the docs folder.
Good that you're asking. The tests are in the flask/testsuite package. To run the tests use the run-tests.py file:
$ python run-tests.py
If it's not enough output for you, you can use the --verbose flag:
$ python run-tests.py --verbose
If you just want one particular testcase to run you can provide it on the command line:
$ python run-tests.py test_to_run
Either use the #pocoo IRC channel on irc.freenode.net or ask on the mailinglist.
See community page for more resources.