Dont upgrade if you're happy. The latest version is 4.20 and 4.21 is going to be out next week. Once it is out, try it out before deciding to upgrade. Make sure you backup your current version so you can rollback if needed. (C: program files\nch swift sound\wavepad folder)
then if you like the newer release you can upgrade at discounted pricing at www.nchsoftware.com/upgrade
Ill post here when the new version is out.