I recently went on a trip to Atlanta, Georgia and rented a car. A Garmin GPS (Global Positioning System) device was an option so I took it to test it out. It turned out it was one of the best things I could have done.

It didn't know where everything was all of the time

On at least one occasion it told us the closest Wal-Mart was more than 100 miles away when we knew it was a matter of a few miles. It figured it out later after we drove around a bit.

Some places it didn't know anything about at all

Mainly mom and pop stores, even if they had been around for as much as a decade. Also places that were outside the Atlanta metropolitan area proper, such as the place we were staying, were hard for the GPS to find. Once we there though it knew exactly where it was. To get there we just put in places that we knew were close by like streets etc. We even had to do this for the Atlanta Aquarium which is about a year old in downtown Atlanta.

Sometimes it didn't know about new construction or road work

We gave up on one location, a thrift store, because apparently it had been demolished and something else was being built in its place.
Another thrift store we couldn't even find but we found one by a different name less than a block away. Maybe they changed names.

It gave less than optimal directions on a couple of occasions

On a highway one day faced with something like three or four different options and a choice to be made in seconds the instructions the device gave were completely useless. Even when we missed the correct exit and came back and tried again we still couldn't understand it. Without a map we would have been lost.
If you miss a turn, more often than not, rather than telling you to make a u-turn or a three point turn the system will direct you to make a much bigger loop, sometimes encompassing several blocks or more.
It gives distances to possible destinations as the crow flies, i.e. in a straight-line from source to destination, rather than via the real route that it gives you.

It's sometimes hard to follow the directions

Optimally one has to listen to the voice instructions and watch the map and read the text on the screen to get the best results, especially if the system tells you to take a left and there are more than one lefts you could take for example. By reading the screen you can see the name of the road you need to take and cross reference that against the signs you see and/or watch the map so you can see the exact kind of turn you have to make.
Deciding when you need to turn is sometimes difficult too. For example the system might say turn in 0.2 miles. I have no idea what that distance is and a lot of times I would turn too soon, before I started reading the screen and checking the map.

Without traffic the projected arrival times were pretty accurate.

By and large though I'd rather have a GPS system than not. A map is great but you can only use it when you already have an idea of where you're going.

When we wanted to get to the closest Wal-mart, or Best Buy it was there, when we needed to find the closest gas station or fast-food place it was there. If we needed to get the phone numbers for all the libraries in the area in order to check their schedule it was there.

When we first arrived in Atlanta for example, the vehicle we were driving didn't have a GPS system and the person who was giving us directions to their place didn't know much more than how to get to the places they needed to go to like their job and the grocery. They had to get their neighbour to try and describe the route to us which didn't work well because the neighbour still didn't know enough about the area to help completely. Most of the other people we asked said that they couldn't read a map. We finally got someone whose information and direction combined with the neighbour's made sense and arrived at the place we were staying.

Once we got the GPS system though for the entire week we may have asked maybe four people for directions and even when we took these directions we never had to ask someone else along the way. It was like having someone who knew where almost everything things was riding along with us.

If I'm ever abroad again I'm making sure I buy one of these devices. I priced it at Best Buy at about $400.00 US and the other popular device Tom Tom was $300 with no additional fees. Considering that we paid about $77 US renting it in a car for a week buying one is a no brainer. It wouldn't work in Trinidad or Tobago I know, hopefully we can do something about that.