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I've used a microwave connection, WiMAX to be more specific, and it worked pretty well. The service I used was consistently 10Mbps+ download, which was good enough for us to us a VoIP telephone system and to do pretty much anything we would normally do online. Surprisingly, we never had any latency issues, which I have experienced in spades using a satellite connection the past. I was at a small business of about 20 people at the time, which is pretty close to the number you have, so it should be fine for your use. I'm not sure how well it upscales, though. We were located in a flat area without any significant tree cover, which is pretty much idea for WiMax, so if you are in a hilly forested region, it might not be as good.