Our flights usually land a bit before noon, so we head to the resort and attempt an early checkin. With Sheraton Vistana, there are a couple of good reasons. If you are early, the line is very short, and it much easier to take time and understand your room assignment, they are more likely to be flexible early in the day if you are unsatisfied with the assignment. If you checkin later you may be stuck with the last units available.
If the room is not yet ready, we head out to the bell station and check our bags so they don't sit exposed in the car while we shop; we usually have an SUV so the bags are exposed in the back. When we get back, the keys are usually waiting at the bell station, but if not, we can check our groceries too. They can keep your perishables cold for you while you hit the pool. When the keys are available, collecting them at the bell station avoids the long lines at the registration area during prime checkin time.
Many resorts offer these same services (bag check, cold storage, early checkin), so it is worth calling and checking before you get there.