If you ride regularly, it won't upset balance,.. but it's not nearly as effective in a tube tire.  Very small punctures only, after that tubes tend to blow out, and slime will just make a giant mess.  I've also had the goop plug up the valve stem and cause a flat while checking tire pressure.  I had to replace the valve because it got so boogered pulling the snot out.
That said, some folks swear by it.  I used it in my dirt bikes because it works for thorn punctures... never get those on the street, just screws and nails... not so good with those...