Autopilots are a NICE, if expensive, accessory.
I used a Simrad Robertson when replacing the drowned out original autopilot on my 48 HATT YF about 1999. It's a time consuming job, but not difficult. When you install one, put in shut off valves at the pump so you can siwtch them off if the pump needs repair...saves bleeding,etc... And check the location where you plan to install the electronic compass...use a hand held compass to be SURE there is no magnetic field nearby....
For unknown reasons, the Robertson computer stopped once and would not start up...I was near Gloucester,Mass and called a local electronics repair place...They said something like "Disconnect the green and gray wires to the AP 300 and touch them together"...you should be ok...sure enough that was the one and only computer problem.
I found the Simrad people OUTSTANDING when I installed and took mine on a set up run...answered my questions immediately right on the phone.Another member here, more recently, was unhappy with SIMRAD help.
The Robertson pump motors (mine was an RPU 160) previously had a problem where permanent magnets might become unglued, touch the armature, and steering would be sluggish, incomplete...Don't know if they fixed that...I epoxied mine and it's been good for five years...a pain, but easy to fix after Robertson people told me that was likely the issue....
GPS interface: Really nice feature; Highly recommended..all you need is the right cable connection between the GPS display and the autopilot. Big advantage when making long runs as you are ALWAYS within say 50 feet of your course because the GPS manages cross track error, so it minimizes distance travelled (and fuel use) . Also, say you head to the Bahamas from Fla, you set your course via the GPS, and it takes you there, right the the harbor entrance or buoy of your choice. Without the interface, you need to manage cross track error manually and adjust your autopilot manually, say as lateral current strength varies along the way....When navigating in fog and currents, like I did in Maine many,many times alone, looking for lobster boats on radar, lobster floats visually, and rock outcroppings everywhere you do NOT want to worry about having to make course corrections as well.....unless you have a trustworthy crew to delegate. Then everybody is nervous!!!