Claimed power production is a bit generous, i doubt it will do what it says in low wind regimes. But it is a professional small turbine.

two-bladed means it has a teetered hub. neither the website nor NREL addressed the issue of how the teetering is regulated. there don't appear to be teeter stops, rather spring compression. could be a weak point in high turbulence. but again, professional design apparent.

both test turbine blades were cracked along the shell seams after some 2700 hours, not encouraging.

small downwind turbines, particularly two-bladed, have been known to move upwind in turbulent yaw, causing the blades to strike the tower. this machine needs investigation on that point, and it's not referenced in the NREL report. i do trust the NREL engineer, who states there are no serious yaw oscillations.

If the owner would be comfortable financially knowing the cost of small wind, as you referenced in the oil drum (but i haven't read, just long experience), he should examine the competition before deciding here.

Gaia has it's pros and cons, but i'd need more analysis before i had an opinion. two-blades have by necessity higher rpm, and are always louder. i am not a fan of deployable tip brakes either, but properly engineered can be effective.

"Life shrinks or expands in proportion to one's courage." - Anaïs Nin