I wasn't looking for a bow thruster, but the boat I liked in all other aspects had one fitted, so I ended up with one.
I didn't switch it on for the first 3 months to make sure I could steer the boat in the proper way.
I've gotta say it's very useful when reversing - especially when there' s any crosswind. Of course it's possible to do it without, but It's more of a timesaver than anything.
When reversing around bends, if the nose begins to swing out rather than correcting by dropping into forward + tiller over to bring it back, which kills backward momentum and requires overcoming inertia to get the boat moving backwards again, a quick squirt with the BT (it takes some experience to know exactly how much btw) and you can continue.
If you have to reverse through a few curves and have some crosswind without a BT you can end up correcting the nose by dropping into forward + tiller over 10 or more times - which requires overcoming the boat's inertia each time - it just takes much longer.
I tend to tackle reversing into/out of spots that ordinarily without a BT I'd think twice about - e.g. reversing in a crosswind from outside the BoatHouse pub in Braunston around the bend, under the double bridges onto the south Oxford, under the roving bridge for a couple hundred yards to moor up.
When I reverse I always challenge myself to do it without the BT - but if there are lines of moored boats it's nice to know that you can get out of trouble - if need be.
Do you need one? No. Are they useful? Yes.