I recommend Twonav GPS
I work as mountain bike guide traveling with groups in many countries all over the world. In the last 8 years I used several Twonav GPS models. This GPS is very reliable, robust, flexible and easy usage, relatively long battery life, and with all the options you need for mountain biking at any terain and location. It uses most gps file formats. With the Land software you can cut and create secific areas topographic detaild map files for the GPS, from several open online maps. And the main advantage is the good support service you get from Twonav. Therefore I highly recomend this product.