Pros
If you want to learn about how an early stage business operates from product to tech to finance to strategy, an internship here will allow you to experience all that. Interns are given real work, and a high degree of ownership of projects. You'll work with smart and experienced people across 3 countries and everyone is very willing to teach and share knowledge. I learnt a great deal in 5 months on product management and web analytics (Google analytics, AB testing, Agile & Scrum, UX, CMS, CRM). I worked closely with the CPO who is an amazing guy - super experienced, fun, dedicated, smart and thoughtful and other interns who were also both smart and easy to get on with. Overall, a good stint and an invaluable learning experience.
Kontras
There is some truth in what the other negative reviews mention, but as an intern, such issues would be rather irrelevant as you are not a full-time staff. The internship is what you make out of it, it is not super structured but this is a startup where everything is fast moving and would not suit someone who needs to be spoonfed. Depending on the personality, this could be a con, but to others a pro. The only con which should be noted is that HK is very expensive and the internship salary won't cover all your expenses so be sure to have some savings to subsidise the internship.