It depends on what species you are catching. I use totally barbless hooks for GT's for example, and don't lose fish, although it is crucial to keep line tension at all times. We should do this anyway when fishing regardless of whether we are using barbs or not...
For tigerfish, with very hard mouths, I like to flatten the barb a bit to make penetration easier, but they jump and shake their heads vigorously, so I don't want to totally flatten the barb. I end up crimping it about halfway down, and that seems to work well.
With circle hooks you can flatten the barbs regardless, the barb serves no real purpose and is just a hindrance.