The stern was never really the problem for me. What I found, is that the pivot point of the boat, i.e. the axis around which it turned, was directly under the mizzen mast.
The problem is, that the bowsprit is 40 feet in front of that point. So any windage in the forward part of the 50 LOA tried to blow the bow off. The further out the windage, the more leverage.
Basically, my bowsprit acted as a unidirectional wind powered bow thruster.
I got used to taking it into account, and getting really good at pausing at the helm and playing the multiple vector game in my head before untying the lines (in order!). I suppose with a stern thruster I could crash into a dock broadside, instead of just with the bow and decrease the risk of snapping the sprit off, but that's a marginal gain.
The only time I really needed a stern thruster was when I poached a slip for a few minutes to get fresh water, then found that there was such a strong crosswind coming from the starboard side that I'd never be able to back out and swing the bow around to starboard. There was also a current running in the fairway port to starboard which would catch my stern as I backed out and multiply my starboard prop walk. Basically, I appeared screwed, or perhaps could try and back out and give in to the starboard trurn and hope to back all the way down the fairway (you know how these boats back) with the wind and current.
What I ended up doing was hoisting the mizzen and sheeting it flat amidships, and backing up. The mizzen became my unidirectional wind powered STERN thruster to counteract my unidirectional wind powered bow thruster (bowsprit) and it worked marvelously! My stern was turning to port, and when I no longer needed port stern thrust, I blew the mizzen sheet.
If I had a bow thruster, I never would have had the "opportunity" to be so creative, and test my theories of docking in real time in crowded places. Minniwaska's point about keeping your regular skills up and not using a bow thruster as a crutch is well taken, but if I do buy a boat with a margarita maker up front, for a while at least, I'm going to be using it with every docking just for the novelty. Expect to see boat dressage in the marina!
MedSailor