Keith ............ Get the thruster.
We ordered one on our 2000 450. I hesitated due to the money. My wife push to get it and she won, but I was the big winner.Our situation may be different from yours. We are moving on board later this year to live, full time for a minim of 5 years. We intend to cruse from Canada to the Caribbean by following the sun. Our current slip in the Chesapeake Bay does not require a thruster. IF this was to be our main location I would not have gotten one.You need to remember a few things:1st, these (450 / 4600) are big boats with lots of windage.2nd, you have little or no turning or pointing of the bow until you get some speed or water passing around the rudder.3rd, when docking or slow close quarter maneuvering it is like having a 2 extra people or spotters on the boat.The bow thruster is very easy to use / operate. It will easily swing the bow of the boat. I have docked the boat at several locations where the "peanut gallery observers" are all deck out waiting for some boater (usually a husband & wife) screw-up so the arguments and yelling can start. Then the docking situation is made simple by using the thruster and the "peanut gallery" is just pointing and marveling at how easy it was to dock this big boat in a little space due to the thruster.I can not tell you how easy it is to use or the normally difficult maneuvers in close quarters you will do like a professional - all the time. We also have a 3 blade MaxProp on the boat. This prop allows the boat to back up in a straight line (no prop walk). So between the two, docking is easy. I find that in close quarters I will usually center the wheel and adjust forward or reverse power and turn the boat ONLY with the bow thruster.Sailing / Motoring performance is a little tougher to tell. I have not sailed a 450 for any length of time other than our boat. When sailing or motoring - I see or feel no difference. Scientifically there should be a little drag or loss of speed due to the tunnel, but it must be small. When I motor the boat (75 hp, MaxProp & Clean Hull) I cruse at 8.2 - 8.3 kts @ 2,750 rpm. The hull speed should be around 8.44 kts (Sq.Rt. of WLL -39'-8 x 1.34). At full power (3,450 rpm) I get 8.7 to 8.8 kts. So realistically when motoring above 2,750 rpm's, I am just burning extra fuel while gaining little in speed due to hull speed limitations. All speeds are based upon SOG from DGPS w/ no tide or current and smooth water. Bottom line, if you can afford it, get it and you will not be sorry.