Iam a customer of Zerodha past one year. Theeir two trading platforms pi and kite are just awsome . earlier they had some bugs in pi . later they fixed it . Though I used only webbased platform kite . its quite simple and design and execution quality ensures fast and exact execution of trades! Perticulary with Bracket order and cover order!
Next their brokerage is very less . often I used to get very low brokerage 24 rupees(including taxes etc) for a mini lot of crude . . finally I really like the kite than pi. Its very fast and accurate . charts are awesome quality!