SBDATA is just the database itself, the policy objects etc. True, nothing in the program directory is irreplaceable, but it's convenient to have that as well, as it contains your connector settings, window layouts, server credentials etc.
As I say though, all that can be recreated pretty easily, but for another 100MB or so of data, you might as well back that up occasionally as well.
Don't forget your application folder. A lot of settings are stored there too.