I am using Tata Indicom with speed 128kbps, unlimited data download plan for the last 5 months. It has generally been reliable and good. I have a wireless modem and use it for my laptop and desktop simultaneously, as i am following the commodities and NSE together. I find the speed adequate for intraday data feed.
The customer service needs is horrible, very pathetic. So if you face downtime its trouble. For this I have BSNL 256kbps Broadband as a backup connection, data download is 1GB per month.
Often in our area BSNL service is erratic, hence have Tata as my primary service connection.