I like my Garmin eTrex 30. It doesn't have a very high resolution display, but it is in colour and you can add additional maps (OpenStreetMaps has them for free!), plus the batteries last for a long, long time. And it uses both GPS and GLONASS，so it locks onto satellites quickly and stays locked on even in very sheltered locations (good for Shanghai because there's a lot of skyscrapers and elevated structures like highways that make it difficult to get a clear view of the sky).