I'll add a bit. I've had spotlock for a long time now, starting with the original Terrova and then moving on to the gen 2. The one Tony has is gen 3. Gen 3 is amazing. It keeps you soooo tight to one spot. The lift assist is great and the "jog" feature is sick.. I am jealous of those features and the "button" on the foot pedal for spot lock. Why they didn't do that to begin with is beyond me (inside, I don't want to believe it was so obvious but gave them something to add to future models).
Yes it works as advirtised. Yes the newer, the better. That said, whatever you can afford GET IT. Spot lock is the single best feature on my boat and is used more than anything on the boat. CO is windy and there's been countless times I've been on the water when no one else can. I've planted on a point with the wind blowing 25mph into the point. Sat on the back of the boat casting to the point, slaying smallies without being uncomfortable.
Here's a few things to consider, aside from the obvious ... you are trolling with the gas motor and hook a monster... best thing you can do is go to deep water and spot lock. It's so great to forget about the boat when you are handling and dealing with a big fish. Lines tangled? spot lock and fix it. Wanna cool off and go for a swim? Spot lock. NEed to re-rig? Yup...
I'm not trying to over hype the concept, I just know this, and I speak for a lot of my friends. I would rather fish out of a 25 year old boat with a 60hp motor and a Terrova (or comparable unit) than I would a brand new boat with a 200 hp motor with a standard trolling motor.
I fish through horrid conditions, and have landed some incredible fish in those conditions. I can't think of one other piece of equipment that keeps me fishing longer, helps me catch more fish than if I was without.