I did a 2-tank night dive with Kona Honu Divers back in the end of May. The first dive really is a chance to acclimate you to the dive site, as well as give you a chance to see some of the fauna that inhabit the site by the daylight. The second dive begins after the sun has set; this is when you get a chance to see the manta rays performing their underwater ballet. I had a blast on both dives. That said, it also looks like at least two other dive ops shared the same site, so you don't necessarily have to book with Kona Honu Divers in order to do this particular dive.
As for my trip, I really enjoyed my dives with Kona Honu Divers. The crew was friendly and helpful; the ship held 12 divers comfortably; during the briefing the DM whipped out a dive book and showed us what we were likely to see underwater (and we saw many of the fish he pointed out!) during the dive; and during the dive he DM also pointed out some of the more rare fish that many of us would otherwise have overlooked. The diving conditions for the first dive were excellent; the visibility was phenomenal (probably round 20-25' by day), the fish were sufficiently abundant, and just before I surfaced I spotted 2 manta rays gliding effortlessly around 20 feet away.
The only negative to the dive was that I had problems with my reg (I rented theirs) that became really noticeable during the second dive. Depending on the angle of the reg, the air was delivered from a range of "free flow" to "not at all". With the reg's mouthpiece pointed vertically downward, I couldn't get any air at all; with the reg's mouthpiece pointed vertically upward, I couldn't get the air to stop flowing; with the reg's mouthpiece kept in a horizontal plane, I was able to suck up just enough air to keep me alive, but with a burning sensation in my lungs still. I didn't notice the reg problems as much on the first dive, since we swam around a bit. On the second dive, since we sat on the bottom looking up, I really began to notice the problem. I "cured" the problem by looking down repeatedly to get air when I needed it, and looking up at the mantas as they glided overhead the rest of the time. Since no one else seemed to have complained about their regs, I think I may have just had a faulty reg.
In the final analysis, I'd still be willing to dive with them again, in spite of the reg problem. However, I'd also be willing to look at what other dive ops had to offer. More importantly, though, I think I would also include the recommendations of the SB forum contributors as part of an informed decisionmaking process for any future dives off the Big Island (I didn't know about SB until after I returned from my HI mini-vacation).
Happy diving!