I wouldn't necessarily say that "you are at the mercy of the islanders..."
Each cruise line makes its own tendering arrangements. Some lines do better than others, based on what we observed on January 13, 2006. RCCL used inter-island boats, "normal" tender boats, party boats and some of its own lifeboats. On RCCL, those with excursions purchased through the cruise line get the early tenders. On Rhapsody and Splendour, there was an "early bird" tender if you really want to try to beat the crowd. If you have made your own excursion arrangements, you have to queue up for tender tickets (which were never collected) and boarding may be 9:30-10:00 a.m.. However, our loading was quick and the actual boat trip is just 5-10 minutes. (Almost 400 people were on our tender.)
Rhapsody - W. Caribbean - 2004; Rhapsody - W. Caribbean - 2005; Sovereign - Bahamas - 2005; Enchantment - Canada/NE - 2005; Rhapsody - W. Caribbean - 2006: Vision - Alaska - 2006
Navigator - E. Caribbean - 11/2006
Vision - West Coast Repo - 4/2007
Grandeur - Canada/N.E. - 9/2007
Voyager of the Seas -"R"W. Caribbean - 1/2008