If read carefully, both Yelp and TA are invaluable sources of information. You just have to know how to filter out the cranks and crazies (not to mention the fake reviews).

TA is also the best place to post a negative review if you have a problem with a property. Most properties will follow-up based on a negative TA review, even after complaints made directly to the front desk or GM were ignored. I've gotten refunds and free nights based on negative TA reviews, after all other efforts had failed.