I am using zerodha brokarage firm since 1 year so I give you honest review on this firm.
First Zerodha is discount brokarage firm so they take less charges than any other brokarage firm of India
Opening process of Demat and Trading account is very fast and easy. You can open account even your adhar number also from online.
Zerodha kite application is good and easy to use.
Main Drawback is zerodha have so much technical errors and always server down so traders loses so much money in intraday trading and customer support is also very bad.
Overall Zerodha is good on only discount brokarage purpose but not for technical and server purpose.