Any driver that uses the auto rerouting feature in GPS devices is putting his or her driving career on the line every time they use it, as it can easily route you down a residential area, restricted route, a road with a low clearance, a low weigh limit bridge, etc. as easily as it can route you correctly.
The auto reroute feature is great for 4 wheelers, but for 73-foot long 18-wheelers, it is a fine or an accident waiting to happen. Thus, I would never use any GPS product unless it provided a way to turn the auto-rerouting feature off.
As both a truck driver and a pilot I have to say that I am amused by this thread and the opinions involved. And I give all due respect to everyone here. Especially since I am a rookie when it comes to driving a truck. But...
A good pilot / driver will avail him / herself of any and all tools available, but be wholly dependent on none. The one tool you can rely on is planted firmly between your ears.
That said, I actually own this unit. And, living in New England, I have to say that so far this unit is fairly accurate. It is not 100% accurate, and I don't think any of them will be. From experience, this unit has had a couple of one ways backward in Boston ... but not many. The mess that is the Big Dig up here is accurate as near as I can tell. But I haven't had the chance to use elsewhere ... yet.
I have a large collection of maps, both computerized and paper. I use them all, just as I use computerized and paper charts when flight planning.
I for one support the proliferation of GPS devices in trucking. And I expect that in the future we will be getting directions to new shippers / receivers with GPS coordinates. These devices are supported by large staffs of programmers and cartographers that do nothing but work on updates. I have, and I'm sure that some of you have, seen the 4 wheelers driving around with a ton of equipment attached to the roof of the car. From what I am told, these cars are actively testing changes for GPS routing, as well as providing the video that allows you to get a look at a street while using something like Google Maps. I'd imagine that this feature will be added to the GPS units at some point. It's already something you can use with your iPhone if you have an internet connection.
One last thought, if the tool in question allows you to be better informed, and thus a safer driver, wouldn't you be a fool not to use it? Imagine being able to know ahead of time if the Sisters are going to snow you in on the road staring at a Highway Closed sign.