"The Garmin 670 is extremely simple to use. While the menus are laid out in a logical fashion, unless you use them often (and I do not), when you need to find a feature, it often takes some time to figure out how to tweak the unit. That said, as long as you remember that you can always back out of menus and will never cause harm to the unit by selecting the "wrong options", moving around the menu system is fine. I cannot imagine a more user-friendly system, even after having tried other manufacturers' units.
Before buying this unit, I had used a smaller Garmin with voice output and had appreciated the way it worked. Since my ownership of this unit, I have identified a few weaknesses that should be mentioned. First, the FM traffic information is relatively poor, even in a large city like Los Angeles. Another issue (and this is more a matter of mapping software imperfections), the unit bases route selection on an algorithm involving both road size and shortest distance. In several instances, I have seen this approach route me through very dense traffic areas that could have been easily avoided. It occasionally does not use shortcuts that may require driving through smaller local streets. However, once ignored and started on a known shorter or quicker path, the Garmin does recalculate and issue reasonable directions to use the shortcut.
I travel frequently and have found the Garmin immensely useful finding hotels, restaurants, and other destinations. The restaurant directory is pretty good, but the initial organization for this and the other service finding features is based on distance from your current location. A menu option allows you to select an alternate home point for finding restaurants or other points of interest. I find the information better organized when I use this feature.
The Garmin has a very sensitive antenna, but it is subject to difficulty getting an initial synch on satellites when surrounded by tall buildings. I have found that this is a problem with all GPS units, though, and not unique to the Garmin. If you already have synch on the satellites when you enter a business district, the Garmin can maintain knowledge of its location and provide the desired guidance to get you where you are going.
Again, some helpful features are buried in menus, but simple logic make them easy to find. For instance, if you want to know which satellites are in view and the accuracy be obtained, click on the signal strength icon.
Also, in other reviews, I had read that you cannot select avoidances such as highways. This is incorrect. There are a number of options in selecting the type path you would like to follow, but you need to look through the menus to find them.
The unit, while relatively compact with its large display, is too large to comfortably fit in a pocket. The next generation of units (which was advertised about two months after I bought the 670) are a bit thinner and should address some of this problem. Considering the price difference, I am still very happy with my selection.
I wish the traffic worked better and the subscription service for traffic data was available for less money. Note that only the traffic service has a continuing cost associated with it; all of the other location services are free.
A couple of last wishes that would have been nice and are surprisingly absent. The display information such as speed, time to destination, or miles to destination should be user selectable. The unit should automatically be able to figure out local time when it is brought to a new location. While such a time feature may not be perfect due to the ambiguities of daylight saving time, the process should yield correct information more often than not as this is usually an offset from your home time zone.
All in all, I am pleased with the unit. The cost of the Garmin units without European maps is significantly less, so unless you are certain to be using it regularly in Europe, it may be cheaper to simply rent a unit in Europe than to buy the capability in a unit you will primarily be using in the US."