I regard a mirror is essential on vehicles which are the slowest and most overtaken on the road. The Mirrcycle is excellent, but I've always used the BM Cateye ones on my bikes and find them ok. They use curved mirrors and give a perfectly adequate field of view, but it's important to fit the right one:
The
BM500G is for straight handlebar bikes.
The
BM300G is for drop handlebar bikes.
Like many bike mirrors, they do often need to be reset on setting off, but if used all the time that takes an instant and becomes an automatic habit.