it is constantly "Nagging" you to pay a small fee to get more features.
I haven't tried Sandboxie, but not all nagware is that inconvenient. Some of them may display only a splash screen when you open the program and that has to be closed to proceed. I had one program that was fully functional after a 5 second countdown delay. Once registered (and it was free if you reviewed it on Cnet), that delay went away.
So, I guess what I'm saying is, if you really want to try it, give it a go. To be on the safe side, just make a System Restore and registry backup first to make sure everything is gone, if you do decide the nagware they have is too intrusive.