Nice article & lots of good info for the do-it-yourself types. I particularly like the advice to make your cabin fixtures dual bulb with the option of using the incandescent bulbs when necessary. This is very good advice also from the point of having an installed spare.
We have a large offshore ketch cruiser. I have also done a lot of research on LEDs for our boat. We operate at 24 VDC so the variation in voltage on our boat will be far greater. Control of current through the LED is key to its life and brilliance. LEDs have a cut off voltage below which they will not operate; a design voltage at which their properties will be as advertised. Above this voltage, the life will be seriously shortened. Since most sailboats operate with a variety of charging systems and conditions, it is critical to control the current flowing through the LED. The resister method described is the simplest but has the unfortunate side effect of consuming some of that energy we are trying to save. The resister method works better on low voltage systems where the voltage swings are least, however, there are several other methods of powering LEDs that do control current without as much lost energy. This is essential for 24 VDC systems and operation of 12 VDC systems is also improved. I will not go into detail regarding these but refer you to a few of my favorite suppliers. They have technology help pages that explain the details. We have opted for Pulse Width Modulation (PWM) for many of our replacement bulbs and fixtures. In this control system, there is a high speed switching device that can switch the power to the LED on and off at 20 to 30 kilohertz and controls the on-time to off-time ratio so that the average current allowed to pass the LED is correct. Our spreader lights are Marine Beam http://www.marinebeam.com/ and will operate from 10 to 60 VDC with no change in output or life. Item# SL-10-01. These are like continuous flash guns at 800 Lumins each. They also offer direct replacement PWM bulbs for many standard fixtures. Also check out http://www.bebi-electronics.com/ and SignalMate at http://kimberlitemanufacturing.com/. All offer exceptionally good product and are technically superior to the LED & resister basic system. I have also checked out LOPO lights. They have a very goodd product. It is PWM as well. Consider LOPO if you plan to replace fixtures since they do not sell replacement bulbs.
We have replaced all lights aloft with LEDs. Marine beam had direct drop-in bulbs to fit the incandescent of our Aqua Signal lights including the Tri-Color mast, anchor, and steaming lights. I installed 6 of their spreader lights as well (3 main & 3 mizzen). I added Signalmate deck-level Nav Lights on the bow and stern as redundant back-up. I am working with the good people at Bibi for a special purpose light for the Windex. This should be available soon and may be the only such LED option around. We will probably begin changing out cabin lights this season.
I encourage you to study the various methods to control current to your LEDs. This is key to lowering your power footprint and longer bulb life. I also made a Wikipedia search on this subject and found a huge amount of detailed explanation on the why and how to. If you want to build your own PWM or other control, the method is described.