it will pass a smog test, will sound deeper, and I don't know the laws in your state, but as long as there are no exhaust leaks, it should not be a problem.
Some say the cherrybombs rust out fairly quickly. I don't have experience with them
:edit: oh.... you said stock muffler... I wouldn't do that. If you are looking for a better sound, chop off the stock muffler and get some cheap Summit Turbo mufflers. The cherrybomb is a resonator, kinda like a pre-muffler. You can cut out the stock resonator and replace it with a cherrybomb.
Check the modifications page to learn about installing a cherrybomb resonator