Its the best institute in India and the best for aerospace engineering in India as well. You can take my words for this matter because I too am M.Tech in Aerospace Structures from IIT Bombay.
One thing you should keep in mind is the flexibility that IITB offers its students while choosing their course subjects. One can choose suitable subjects according to his/ her liking. Only core subjects are compulsory which are generally two per semester. Anyways as companies see which all subjects candidate has taken during his/ her academic tenure, this facility is very handy to get your resume ready for right kind of job offers.
As far as my specialization in Aerospace Structures is concerned, the subjects this stream offers has very much similarly to that of machine design stream of mechanical engineering department. Subjects catering to study of composite materials are state of the art. All professors are eminent personalities in their respective fields of expertise.