If you do decide to cut matchstick pieces by hand, make sure you've got a good, sharp knife. It doesn't have to be a $200 chef's knife; it only has to be really sharp. Otherwise, you run the risk of a pretty serious cut on your finger.
Mandolines are great kitchen tools, but again, you have to make sure you're being smart. Watch your fingers. Mandolines are really, really sharp, so using the food and/or finger guard is a good safety precaution.
I think the most common place I’ve seen matchstick vegetables is in Asian food. I see carrots cut like that pretty often.