I use The Uniform Server (TUS) on Win 8 (and Win 7 and XP) with no issues; the default database user name and password (root for both) work. I just did a new install on Win 8 with the latest version of TUS 8.8.3 and WP 3.5.1 ... yep, no problems. Added a plugin and theme ... all is fine :)
I abandoned XAMPP, WAMP and all the others once I found TUS a number of years ago. A couple of reasons for this is that it doesn't install anything on your system; it's a self extracting archive and there is no "registry dust". Plus, it can be run in production, which one instance has been successfully doing now for a year on a Win 2008R2 server running an e-learning script with over 1,200 users.
Cheers!
Lyle