I highly recommend this resort.
Good things:
Units: spacious, beautiful, and laid out in such a way that noise from other units is minimal. Further, they are stocked with most things (other than food) a family needs to enjoy a week away from home. China, flatware, pots, pans, casserole dishes, etc, along with paper towels, dishwasher detergent, and a small box of laundry soap are among the conveniences provided. BTW, hand and bath soap are also stocked, but NOT shampoo.
Housekeeping: Aside from the minor issues noted below, the unit was also immaculate upon our arrival. You won't see housekeeping again during your weeklong stay, but they do a wonderful job in anticipation of your arrival.
Views: both grounds and gulf are lovely and easily seen from both the large patio and, if you have a top-floor unit, from the balcony off the master suite.
Outdoor common areas: functional, attractive, and well-maintained. Awesome grilling areas, including a HUGE (think Argentine steakhouse) grill by the pool, separate areas for volleyball, tennis, horseshoes, and shuffleboard, as well as outdoor shower, footwashes, and sink stations for shell-cleaning. Very functional beach umbrellas can be rented for $1/day, and two sand chairs are included with the unit.
Beach access: three well-maintained boardwalks lead to the private beach area from all sides of the complex. The beach itself is clean, and the water remains shallow for many yards off the shore due to sandbars--great for little ones to safely enjoy the surf.
Staff hospitality: Everyone we met in the front office and around the resort was friendly and professional, and seemed genuinely eager to make our stay a great one. A pre-arrival mailing, welcome materials waiting at our unit, and a newsletter detailing daily events and activities added value to our vacation.
Two minor gripes:
For the most part the units are well-maintained, and the furnishings in particular (mattresses, drapes, chairs, etc.) are in excellent condition. However, our unit in building C was in need of repainting on some of the interior walls, especially in the bathrooms (scratches, dings, gouges, etc.--some painted over, some not.). The dishwasher racks also need replacing, as the rubber has worn off the tines leaving rusty points. Finally, while clean, the master bath had a bit of black mold growing out from beneath a fresh-looking coat of tub sealer, and the decor in the master bath, generally, looked to date to the early 80's.
The outdoor pool was too hot to get into, even at night, on all but one of the days of our stay. It was so much warmer than even the ambient air that I was convinced it must be heated, but the management said it's just the effect of the sun and the humidity. Being from the mountains, I was expecting to use the pool to cool off--ha! This isn't the resort's fault, obviously, but it's something to be aware of if you're planning a vacation in the summer.
I haven't stayed anywhere else on Sanibel, so I can't compare. Overall, though, I think even picky travelers will find that Tortuga meets their expectations. Happy travels!