Is IIST a good option to select to do m.tech in ece
In case you have not got top IITs and NITs, yes it is good.
At IIST all professors are very well qualified and even few are scientist. you will get happiness when you will get the exposure to space knowledge, innovative discussion and diversity in culture. Apart from this, you will get exposure to ISRO real time projects, which will really help you if you are research oriented. Even they have labs better than IITs and NITs.
However, there are few drawbacks also. The first one is placements, but they are working to improve it. It is located far away from the city and in hills, but it can be seen as a plus point because you will get the atmosphere free from the pollution.