I vote no..... emphatically...
A pair came with my boat, it looks like the PO had purchased them at a surplus sale because they were marked with a price of $8.00 on them. I installed and used them for a year or two on the halyard winches. I eventually removed them and gave them to a buddy with my blessing and these comments:
Self-tailing feature- I found they offered me no real advantage because I still had to clear the tail....the grippers are on the underside of the rubber rings...so you have to completely wrap the drum for them to grip the line. That means you get less than one full turn before the tail wants to overlap the loaded side. What is missing is a stripper arm. So, in effect they are not self-tailing. You can, however, make one-handed tightening micro adjustments with the line loaded and cleated in the wincher's jaws.
As a cleat, they work okay. I never noticed any slipping with the line completely wrapped on the drum and cleated in the wincher jaws. However, If you use your halyard winch for other controls, such as the spinnaker or jib halyards... you need to install real cleats somewhere in front of the winches anyway.... so what's the point?
With line handling they are definitely a disadvantage. I would never use them as sheet winches. As stated before, you have to fully load the drum for them to work at all... so if you put less than 5 wraps on the drum, all they do is get in the way. They are especially annoying when you cast off the old line as you're tacking the boat. Standard winches are designed to allow the trimmer to simply pull up on the sheet to pull off the wraps.... you can't do this with these things (any self tailing winch for that matter) because the little rubbery grippy nodes on the bottom of the ring snags the sheet. You must stand over the winch and unwrap the line lasso style... nosirree, not my idea of effecient sail handling.
My buddy was excited to get them free... I helped him put them on... but a year later I notice he had removed them. I asked him about it and he told me they weren't what he was hoping for (told ya) and he got so frustrated trying to remove them he just took a knife and cut them off.
So... even though there are a few who like the winchers... I say don't waste your money. I'm glad I didn't. You cannot turn a standard winch into a self-tailing one this simply. You would serve yourself better by saving a few more bucks and installing a rope clutch for your hayard winch. Definitely an upgrade. Garhaurer sells an awesome double rope clutch for a little over $100. Way... way ....way better improvement than winchers!