Seems I wasn't the only disappointed person who found out WLinstaller sucks on x64. No worries though, I won't have to hack the WLinstaller to get the .msi on my machine. The installer for Windows Liver Writer Beta 3 can be found here, along with those for the other products in the Live Suite.
Almost makes you wonder if the Live Team messed up the installer, or intentionally excluded x64 to promote SkyDrive.