I've been using one for 5 years. I had one on a deep-v w/54" shaft for 4 years and now have one on a bass boat w/45" shaft. Never had a problem with either set-up. Like you I was skeptical. I almost went with the metal slide mount, but I saw somewhere that they can be annoyingly noisy. These mounts are surprisingly strong. I've use that little cotter pin for the retaining clip, no problems with that either. One exception is on trips, I use a pad lock.
These mounts are great if you have to remove the TM for any reason.