I am surprised there is no Starbucks here yet. Vietnam must be the perfect country for them - there really is a coffee house culture. And it is not limited to a coffee: breakfast buffet, lunch menu, cakes, ice cream, you name it. They're places to hang out, and to see and be seen.
Luckily, most have true Vietnamese coffee - a slow drip, brewed at your table, and very strong. A bit like Turkish coffee without the deposit (I am probably insulting two countries now). You can get it hot, but also iced, which means you also get a glass of ice to poor the coffee over. Tasty. In almost all places, you also get free and endless supply iced tea. Though once I got hot tea with my hot coffee; the rest of the place got ice tea with their cold drinks.
To get back to Starbucks: the biggest chain (Highlands Coffee) is very similar to Starbucks. Espresso drinks only (allegedly they have drip coffee, but they are always out), about $2 - $3. Not the best place for local colour (though it is filled with locals). My favourite chain is Trung Nguyen (eight different roasts of Vietnamese coffee, and cool places) but I also like trying all the independent places. Spoilt for choice.