If you loved 'Serious Sam' you'll love 'Will Rock'
If you hated 'Serious Sam' you'll hate 'Will Rock'
I enjoyed it enough, on a purely mindless run 'n' gun level; it's not 'Half-Life 2,' but it's not trying to be.
One other thing: the demo runs quite well. I only have a 700mhz processor (minimum calls for 800mhz), I was able to run the demo at 800x600 with most of the visual details set to 'high' and it ran smoothly.
"Now that's a lot of pussy!" will probably go down as the worst one-liner in FPS history.