I used System Three's LPU this past spring to paint my Alberg 30.
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While I don't have any experience with any of the other LPU's, I can say I'm happy with it. I researched the heck out of these paints. System Three's paint was attractive to me since it didn't require a bunch of specialty thinners, can be rolled-tipped, low voc's and easy clean up.
I bought a quart to experiment with. I painted a few small things, some scrap wood ect. Like any LPU from what I've read, there's a small learning curve to putting this stuff on. I had never rolled-tipped so the practice was welcome. After letting the scrap samples cure a month, I experimented with the paint trying to lift it, scratch it, abrade it and otherwise damage it. I was satisfied enough to go with it.
Tons of prep, we primed with System Three's epoxy primer (get the new formula) and went for it. I had my wife as the tipper, I rolled. Temperature was key. I found the paint was happiest at cool temperatures (70's). When the air warmed up to the 80's under the tarp the paint dried much to fast with little time to tip and flow out. We'd do a coat in the morning and another in the afternoon. I'm very happy with the results.
Is it durable? Well, my boat never made it into the water this past sumer so it never got any real world testing. However I've been working on the boat continuously since the paint job, careful as I am, the paint has been bumped with tools, screwdrivers slipping, parts piled on it with no problems. It appears to be far more durable than the Interlux enamel I used on the cabin interior.
I'd be happy to answer any questions.