We stayed at Reef's End late last April (I have a prior posting from our return from Belize last May). Although my comments are both good and bad, I did enjoy my stay there. First, the food was excellent at every meal, far better than food we had at some of the famous locales on the mainland and better than the "gourmet" food at Chan Chich Lodge. People did not fawn over us, or check how we were, but were accessible and helpful when needed. The beaches were disappointing; lots of litter had washed up on the island and no one seemed to care. We did find some patches of sand to sunbathe, but you will not find long stretches of beach to stroll or body surf. Don't believe what you read about it taking 30 minutes to walk around the island. It's more like 10. Generally, we hung out in hammocks or at the restaurant/bar when we weren't snorkeling. The restaurant has a fabulous view. Having just finished a four month stretch of working almost seven days a week, often for 10 hours or more per day, it was wonderful for my state of mind to just sit there and look out on the clear blue water.
We stayed in one of the cabanas and found it spartan, hot and humid. (but clean) The main lodge (a two story building) is much better placed in terms of catching breezes. When we were there, the lodge had few guests, so it did not seem as if having a room as opposed to a cabana would be noisy. And, we could hear plenty from our cabana, so we didn't feel very private anyway.
As far as snorkeling, we went about three times a day. It wasn't wall to wall fish, but there are plenty of fish to see, including the school of tarpon than inhabits the channel just south of the island.
The boat ride is easy and doesn't take too long. Don't let it discourage you from staying on the island versus the mainland.
Next time we go to Belize (and I hope there is a next time) we might save up to stay on a slightly more upscale island. But we definitely had a great time at Reef's End and Tobacco Caye. Its access to snorkeling and overall relaxation quotient were high. And the other guests were very nice and down to earth. We felt very much at home there.