WiMAX for business internet?

William writes: "Does anyone have firsthand experience with using WiMAX for internet access? Our company is on a T1 line right now and we are looking to upgrade our internet speeds. WiMAX seems to be the most affordable and cost-effective solution in our area [San Francisco], but I have no personal experience with it so far. How is the performance and reliability with WiMAX? I would appreciate any insight you all might have. Thanks in advance!"