A detroit locker will typically remain locked until some external force changes the speed at which a wheel turns. i.e. a turn.
This means that the differential won't unlock until you're already in the turn. This will result in some tire scuffing, and when the diff unlocks you'll hear a bang. Furthermore, a detroit locker resists unlocking whenever driveshaft torque is applied, meaning that it will be less likely to unlock if you're going around a corner with your foot on the gas.
What's more, when you're driving on sheer ice (such as when it's freezing raining) the rear of your truck will be a lot harder to control, as it will want to slide all over the place.
That being said, if you can live with these compromises, it's not such a bad way to go! Just keep in mind you'll be replacing tires a little more often, and you'll have to slightly change your on-road driving habits.
If it was myself, I'd spend a little extra cash and buy a selectable locker that you can control from inside the cab. The only downside to that is that inexperienced drivers can apply tremendous stress to the driveline by using it when its not necessary.