[nomercy400]

My biggest takeaway from china is that people are generally ambitious. There's a vibe of wanting to achieve something, and the discipline to achieve it. Most of the people in the city are young (below 30).

I can confirm on the visa part. Get the right visa. If you are there to work (ie. get a paycheck), you will need a 'work visa', not a three month business/intern visa, as I happened to have.

Shenzhen<->HK travel will count as an enter/exit the country, so if you plan to do this regularly you will need a multi-entry visa.

Other than that, Shenzhen is great. And if you don't want to learn chinese, there's always then shenzhenstuff website.