We have been using Act Broadband(north east of Bangalore) for more than 1 year now and the speed and connectivity has been quite decent up til now. Only recently we are facing little problems with the connectivity. We had moved from Airtel 3G connection to Act Broadband because of the speed that they were offering. In the beginning Act was extremely good in terms of speed. But I guess as more people started taking the connection, the speed has gone down these days. We stay in a large apartment complex and more people using the connection also affects the speed I guess.
Overall, not much to complain given the choice that we have. Nobody(including Airtel who are the most expensive) can boast of excellent customer care or technical support. In this scenario, Act does quite a decent job.