There are cheaper and easier-to-use SWF protection programs out there, but secureSWF is the best one I've found. It will require a little more learning than some of its competition, but it more than makes up for it with the stuff you can do.
Heck, it actually made Pop Pies 3 smaller!
SWF protection isn't by any means foolproof, but in many ways it's good enough for what it needs to do. It's a bit like that joke about the two hikers who come across an angry bear. The first hiker says "should we try to outrun the bear?". And the second says "I don't need to outrun the bear. I just need to outrun you."