I purchased the Tom Tom 910 after a lot of research, because it is simple to use and has many features, including a larger screen. I had little time to practice before taking it on an extended tour of Europe. I found it to be an excellent device, delivering us right to the entrance of isolated camp sites on many occasions. Taking us back to our parked camper in larger towns was an added bonus.
A couple of times I found the maps were not up-to-date - roundabout exits, new one way streets and the odd blocked-off street for example, but concluded it was my fault for not updating on line before we left home. However, Tom Tom soon got us back on to an alternative route. I have still to master that job. An expensive gadget but well worth it. If you don't programme it properly, of course it will not work.