My sister is an alumnus of IIT Mandi and her experience at IIT Mandi is what motivated me to write this answer.
Cons
All in all, IIT Mandi has a very happening campus life that will leave you with millions of memories.
IIT Mandi offers an enjoyable college experience. The campus is small and beautiful. The north campus and south campus are separated by a mountain. If you like being in nature, you will certainly enjoy your time here.
The faculties are well-experienced and helpful. You can approach them, regarding any of your problems. The lab facilities and infrastructure and good enough to back up the course projects.
Under the Startup India campaign, IIT Mandi has been selected as one of the Technology Business Incubators. To encourage good startup ideas, the institute has set up initiatives such as Catalyst. This helps budding entrepreneurs with securing funds, offering in-house consultancy services, and giving access to necessary resources.
My sister is a student of IIT Mandi. So, I can tell you about her experience of attending the institute.
You have a mixed feeling staying in IIT Mandi. You will meet good people, make a few friends for life, and a lot more. Overall you can expect a life-changing experience.