Laptops are obviously expensive devices, so if you're traveling anywhere where there's a risk of it getting stolen then you might want to think twice about it. The other risk is the laptop getting damaged when you're traveling, so we'd suggest a padded case to cover it within your bag, plus you may want to think about a laptop designed with ruggedness in mind (we have one such selection in our guide).
If you're doing a regular, safe commute though then a laptop can be very useful indeed to maximize your flexibility and the efficiency of your working time.