Immediately after installation of SilverStripe I am redirected to the login page. However, upon entering my UN and PW (of which I created moments before) it prompts "That doesn't seem to be the right e-mail address or password. Please try again.". I have tried 4 reinstalls.
Whilst I don't have an answer for you about the problem you are seeing (usernames and password "Just Work" for me on install) you are able to set a default user name and password in configuration so that you can keep moving without re-installing everytime.
Put the following in to mysite/_config.php
This will force the default user admin user to be 'admin' , with a password of 'password'.
Anyway, this should get you past this problem without needing to get dirty in the database to ensure that your initial user has been created.