For local development we have moved our recommendation from IIS to wamp or xamp simply because it is easier to install either of those than to install IIS 7, then configure it for PHP and MySQL.
The installation process from Wamp or xampp is much quicker and easier.
it is not necessary to have a local testing server, but is can span development time up.
If you do not want to install a local testing server, you can simply upload the power store files to the remote host after configuring the WA_Globals.php file and the database connection file.
the .sql script that comes with power store will not create a database, but will create tables in a database that exists on your mySQL server, you can either create a new database for the PowerStore tables, or use your existing one.
Where yo want to set power store up on multiple domains, you just need to upload to each domain, make sure that the WA_Globals.php file and the database connections file are set properly with the information on that domain.