I too have the Ultrex 80lb, and have had it for almost 2 years.
I love the thing and has been by far the best money I have spent on my boat (and I have spent quite a bit!!).
The spot lock is an awesome feature, specially in strong winds, but when there is very light to no winds the it can be quite annoying, as the whole things keeps steering left and right constantly.
The last few trips out my spot lock would shut off all by itself when the motor turned to full right. It was only yesterday that I realized that there was something trapped under the front of the pedal, and the pedal was hitting it and shutting it down. I found it yesterday and removed it and now it works fine again
I got the 52" shaft for my 18.5' Triton, and if I was buying all over again I would get the 45" shaft as it does stick up rather high and occasionally interferes with casting and hook sets.
Having said all of that, there are several guys over here using the Garmin and Lowrance trolling motors, and those things appear very sweet, mainly due to the very quiet steering. The Ultrex can be quite loud.