Source Filmmaker, on the surface, seems to be just like every other animating program you could get.
When you start getting into the meat and fat of this program, however, you will soon see how often you can find yourself yelling at a computer screen because a single thing broke that melted down your animation.
Whether or not this is a keyframe that went wrong, a transition that stuck through when you did your keyframes, sound being distorted, or any other thing, it's a pain to get back into the animating mood!
While the Source libraries have an impressive library of sound, if you require something substantially more cartoonish or anything of that sort, you'll need to seek out sounds on your own. They don't usually carry those kinds of sounds on their library, though with the Steam Workshop, a lot of what was missing can be used. Most of the sound files you'll deal with are WAV files, but I don't recommend trying to impliment your own sounds, unless you want to hear screeching white noise output.