Ipilot is sweet, I love mine, but it is not without limitations.

Spotlock doesn't keep you locked to the spot. After you've drifted a ways, it will race back to the spot and overshoot the position. Not worth a darn if you are trying to sit on a spot as the lines will be near horizontal as you race back to position. I use mine mostly to hold steady as I retie jigs while pushing.

Auto pilot zigs and zags when you are pushing or anything at slower speeds and some wind. I haven't noticed it when pulling or at slgihtly faster speeds.

I still love using it, but it doesn't do everything that I envisioned that it would. But still much better than what I had before.