We replaced the traditional stuffing box on both our Sabres with a PSS shaft seal. It's what Sabre installs on their new boats. While the issues that others in this thread raise are valid, they are of low likelihood. We have never had an issue with our PSS, I check the bellows regularly, and made sure that the area around it was clear (should be anyway since there is a spinning shaft). Besides being dripless, another benefit of shaft seals is that they reduce the effects of minor engine misalignment since there are only two points holding the shaft vs. three with a stuffing box. The effect is increased cutlass bearing longevity. I don't plan to go back to stuffing boxes; if shaft seals are good enough for the Navy, that's good enough for me! IMHO, stuffing boxes are more worrisome because you always have to keep after that drip, and I HATE
leaks of any sort!
I describe the benefits and process to install the shaft seal in the following two links:
Black hose on stuffing box
cutlass bearing on 1968 Islander 33
BTW, I agree with others that flax in a traditional stuffing box should be avoided. Use the synthetic stuff. Flax is the traditional material because they didn't have anything better in the old days.