In normal driving the two speed pedal operated gear change works very well. It gives a very simple easy gear change enabling you to nip up and down the gears with a minimum of effort. However it does have its drawbacks. The obvious one is the large gap between the gears, there are some circumstances when bottom gear is too low and top is too high. A Ruckstell two speed rear axle alleviates this to some extent.
Places where you may find difficulty are:
1. Changing up a gear on hills.
2. Going into junctions or roundabouts (traffic circles) where top gear is too fast.
3. Going over rough ground or grass.
All that can be done is to grind along in low gear until top gear can be used again. The only other answer is to install an auxiliary gear such as the Ruckstell two speed rear axle.
In practice a bit of coasting around obstructions and then with a quick burst of low gear before going back into high again will negotiate most of these situations with ease.