We have gone over the Labor Day weekend a couple of times, and had great weather. Not nearly as hot as our July or mid August trips. The resort had a good crowd, not crowded. We only purchased the trip insurance once, and are quite a bit ahead by not spending the extra cash. We have never had to cancel in over a dozen Cancun trips.
Same as us Bart, we always go over Labor Day (past 8 years) always had good weather, but we have been lucky as we dodged hurricanes a couple times. We have never bought insurance, we will get caught someday but for now I would say we are ahead. We love it at this time of year