My company is thinking about doing this. What should I be prepared for? What do I need to watch out for and be careful of when working with these offshore devs?
As an outsourcer with 25-year experience, i think outsourcing is always a bad idea and even desire to turn to it says that something in the company is seriously rotten and it will probably head south pretty soon anyway. It just doesn't work because objectively incentives for outsourcer - whether individual contractor or a company - in fact individual contractor is a lot worse, unlike normally believed - are fundamentally misaligned with those of the client. For a full-time employee with job security and stocks, they can be more or less aligned.
As always, depends on the company you deal with. Some can be shady, some not.
Vietnamese culture is fascinating and lovely, they work super hard and there are a ton of really smart engineers there. But they also do things a bit differently and it'll all gel depending on how westernized they are in their thinking.
CodeLink and EastAgile are the two companies I'd work with. I know the founders personally as business and as friends. Really solid great people.
You should definitely work a deal with your company to go visit.