Not all that bad...
The game was an interesting concept. One problem that I had with it was that it was too tall; I had to press F11 to get Firefox to be large enough to accomidate the whole screen. Unless you are one of the few rare people with one of those monitors that can flip up vertical like a portrait, it would be smarter to align the screen horizontally so it fits on everyone's monitors without reducing the gameplay space.
I thought it was particularly interesting how the levels were set up; were they randomized? I nailed Waldo once when I just saw the bottom of his hair, first shot.
That said, all around a good game that just needs a few things tweaked.