Hi Zander,
I have a Raymarine ST1000 on my 235. Its quite old, i.e. it was on the boat when I purchased 7 years ago. I had to have it repaired once (£180) it got wet and decided to give up the ghost Works fine most of the time then on occasion, for no apparent reason, goes off at a tangent, needs to be re-set, then fine again.
I don't use it all that much - I sail mostly single-handed; drains the battery and takes all of the fun out of it, for me at least.
I much prefer a 'tiller-tamer' which I use when not at the helm and this works fine. So long as the wind is not too serious I find I can move about the boat/below and it retains its course.
Hope this helps