Top positive review
Only con so far is the total lack of documentation
December 9, 2016
Looks like a good product, just installed mine.
Before installing, I opened it and checked its insides (see pictures); I'm not an EEE, but I have some electric/electronics experience and it seemed well built: all-metal box solidly put together with 8 screws, still easy to open with just a screwdriver for inspection/maintenance/whatever, fiberglass circuit board instead of the cheaper phenolite, and solders seemed solid and correctly done.
Examining the circuit board closer, I saw two soldered-through 6KE68CA (the larger black pieces near the center). Searched a little and found its datasheet, they are supposed to be "600W TRANSIENT VOLTAGE SUPPRESSOR", which is exactly what a quick-responding spark arrestor should have. Additionaly, there are 16 SMD-soldered smaller pieces, 8 for each RJ-45 connector, ie, 1 for each of each connector 8 pins, all of them labeled as only "M7". Wasn't able to figure out what those are, tho.
Been in operation for about an hour: ethernet error counters on the respective interface are all zero so far, so it isn't introducing any issues.
I purchased this specifically because of the metal box (I've seen plastic surge suppressors catch fire in the past and almost setting fire to the building, so I'm not risking anything with plastic here) and so far I have a good impression of it. Will post again in a few months if anything else shows up.