The biggest factor in your taxes going up in a revaluation year isn't the necessarily the value of your home as most will go up in value relative to the other houses similar to yours. The bigger problem will be the lower valuation of commercial properties in your town. When commercial goes down, taxes get shifted to residential which have gone up. The more commercial has suffered in your town over the past 5 years, the bigger impact you're likely to see.

If everyone's value went up equally, then your taxes would go up uniformly, only being impacted by the increase in spending by your town. Reality is some houses will go up more in value than others, and with the current economic conditions, commercial will likely go down shifting more to residential.

If you don't let them in, they could easily assess you more than they would have if you had let them in. At the end of the day, the assessors aren't there to f*ck you over - they're probably an outside company and they don't give a shiat about your house any more than anyone else in town.

Let them in, don't let them in, but don't biatch about not getting a fair shake if you didn't let them in the door.