The Twinkie has a Century 2000 with altitude hold. It holds altitude within 10 feet, heading within a couple of degrees and is absolutely rock solid in approach mode. In fact the first time I flew a coupled approach I thought something was wrong because the needles were so solidly centered.
An good autopilot is one of the most sophisticated and powerful pieces of equipment in an airplane, and unfortunately it's proper use is usually treated as an afterthought. If you fight it, it can literally kill you by trimming the airplane against your control inputs. The keys are to understand exactly how your unit operates, to pre-flight it correctly, and if it is not working to get it fixed.
I like the Century, it's attitude based system is more solid in bumps than the rate based STec, but if I was putting a unit in an airplane with one vacuum system I'd buy an STec to back me up in case of vacuum loss.
Jay
Agreed in all respects. I like the rate-based S-Tec as a backup to the vacuum gyro instruments.
Have seen, in the course of my shopping, more than a few aircraft with both a full-featured autopilot (2-axis, attitude-based, like a Century IIIo r 2000), and a rate-based wing-leveler (Century 1 or S-Tec 20 / 40).
Belt and suspenders? Yes, thank you.