After considerable research, I decided to go with the 2512iX - we live aboard a boat, and power conservation only goes so far, and we like our creature comforts.
The booster seems to do what it is advertised to do. While I haven't let the battery bank get too low since I installed the unit, I do see a 4 to 10% boost in charging current when there is enough sun to do some good. I have an A-B switch, so I can quickly compare boosted with unboosted charge current.
My big problem with the 2512iX is that it radiates copious amounts of RF energy, aka EMI (electromagnetic interference). This has made one of my VHF radios almost useless, as the squelch can not be turned high enough to quiet the receiver, and even if I could quiet the receiver at the to of the dial, I wouldn't be able to hear any other station. Most of the noise seems to be on or near channel 16, the safety channel.
I contacted Blue Sky, but beyond suggesting moving further away from the unit, and grounding the case, their answer was "that's the nature of the beast." Their entire reply is at the end of this.
I have a metal enclosure totally surrounding the 2512iX, bonded to the boat's RF ground plane. I have installed EMI suppression cores on each wire entering the enclosure as close to the enclosure as possible (~1/2 inch), and still get severe interference within 5-6 feet of the unit. Unfortunately, it will be hard to relocate the booster and keep electrical runs reasonably short - the radio has to stay at the navigation station.
Rating the unit is difficult: a 4 or 5 for energy efficiency, a 1 for EMI that was never warned about or expected.
Quote from Blue Sky:
The 2512iX has at it's heart a DC-DC power converter which can produce some noise (EMI). Whether the noise presents a problem in a given situation is very installation and application dependant. Things that can help reduce noise include grounding the 2512 case, grounding the PV module frames, and trying to the extent possible to keep radio equipment and antennas away from the solar system. If the noise has always been there this is likely the nature of the beast. If it has suddenly appeared and you have not lost a ground or incurred another noise increasing problem it is possible that the unit has failed in some manner.
We are presently working on a solution to reduce VHF EMI but do not have one at this moment. I will keep this communication on file and inform you when we determine a solution.
Richard A. Cullen
Blue Sky Energy, Inc.