I did a couple of dives with Red Sail last August. We stayed at the Hilton Waikoloa - I had been wanting to try one of the operators in Kailua-Kona, but went with Red Sail only because they were located on property. We were only there for a 3 day weekend, and I didn't want to be driving into town every day.
I wasn't able to find too many reviews on Red Sail's operation, and what I did find was so-so, so I wasn't expecting too much.
However, I was very pleased with my experience with them. I stopped by the shop the day prior to my dives and filled out my paperwork with them (since I was passing by anyway), so I didn't have to do it the day of the dive.
They pick you up at the downstairs lobby and shuttle you over to a nearby beach where they launch off of. There is a bit of a walk from the drop off point to where the boat is - maybe a 50-60 yard walk down the beach. This is one of the complaints I had read about, and I can see if you were hauling gear it might be an inconvenience. Since I didn't want to bring my gear for such a short trip, I was renting almost everything and the walk wasn't a big deal. You have to wade out into the water to get onto the boat - if you want to keep anything dry, be sure to put it in the "dry bucket". When you wade out, the sand drops off abruptly from knee high to waist high before you reach the boat.
The boat is one that I've dived off of before in Honolulu - the Lio Kai, I think the name is. It was one of my favorite boats in Honolulu and I was rather surprised to find it in Kona. We did two shallow reef dives and they were excellent.
The cost of the dives themselves is pretty comparable to what you'll find elsewhere in Hawaii, but the cost of the gear rental is a little higher.