has any one had much experience with something like the Raymarine ST1000

just wondered how it would go in 15+ knots on a 27 foot yacht

Simple answer ..not for long...
My boat came with ST1000, boat is smaller but if I pushing hard
my tiller is exhausting exercise. Upgraded to ST 2000 no problem there.
Guess it comes down how the rudder is balanced.
I used to sail 32 footer and tiller was just perfect.
I can only recommend ST 2000, you need extra torque.

Another vote for the st2000.
They are handy, but they aren't "set & forget", you have to treat them like the fragile piece of kit, that they are.
Don't let them work too hard (in strong winds & choppy sea state) for too long.

St1000 here, 26ft 2t. Fairly well balanced but not perfect due to the transom hung rudder. It has always performed well.

There are many in use on another website for similarly sized boats without problem.

THAT IS as long as you don't get either model 1000 or 2000 wet with spray or rain. In collects at the electrical compass and then zilcho. The other issue is they have no bump stop so if they are hard helming at full lock then they overheat frying the wiring.

I have a waterproof sock to keep mine dry and out of the sun. Grey isn't a friendly colour in the tropics... As for overheating. If you're steering at full lock then you need to balance your boat or put a reef in. Ideally the autopilot should have bump stops but more ideally you should be sailing not scrabbling along.

In my research the Simrad has scored more negative reviews, FWIW YMMV.

I have also got a wireless key fob so can activate and deactivate and change course from anywhere on the boat. Now that is a real autopilot. they are available from madmanmarine. V happy customer of both items.

I have the Raymarine Evo 100 tiller on a 26'. Transom hung rudder also, it steers well but needs to be on high setting running in seas under kite.
I was surprised to find they use a ST4000 drive, as the 100 is the smallest autohelm in this range, I expected it to be a 1000. The 2k and 4k are the same worm drive and it sure steers and tacks responsively enough!

Thanks for the comments.
Our boat is a Northshore 27 with a transom hung rudder. You need to reef in anything over 18 knots otherwise it has a lot of weather helm. I still think it would work well as long as conditions are not too extreme.
Need to be conscious of power consumption with a 40W solar panel and a 105Ah AGM.