I've used the Tillerlock clutch on my Catalina 25 for three seasons now, and I LOVE it.
Very intuitive; even nonsailors first-timing on the boat don't question "How's this work?".
Rugged design; no maintenance problems.
Easy to use as a brake, not just clamping in one position but taking some rudder pressure off hand-sailing.
To neaten the installation, I routed out a shallow, flat-bottomed indentation in the top of my rounded tiller.
Occasionally use our Raymarine Tillerpilot autopilot for longer passages, but seldom now bother to get it out and mount it, because the clutch is always there.
And of course it's super easy to lock the tiller amidships when leaving the boat on its mooring.
Joe - s/v Assignment, Catalina 320