Top button is a good thing, but only for a single button that can be easily reach (eg Polar watches).
In the GT-11 case, all controls are made from the top. As the product is fully sealed, the joystick is rubber covered and small so when doing sport it is difficult to handle correctly. In addition, you navigate in the menu with the joystick and you validate your choice by pressing on it. Another annoying thing is the escape button that is also power off, a short press is escape, a longer is power off. But during exercice if you press too long or sometime a second press to be sure that the first have been taken into account and POUF ! you switch off your device.