I've been using navigation and route-findiing software since the early days of Autoroute. I had a rather unofficial copy of version 2 which I liked to much I bought the latest one and kept it up to date, right up the to Windows 3 edition which used the improved graphics capabilities to provide much better maps. It was an excellent program and it was a great shame that, having bought it, Microsoft didn't know what to do with it and killed it off. I also had it on the Psion 3 (the deal went through just before the MS buyout), which gave me an on-the-move implementation. None of these was an actual navigation system, of course, but were all handy for estimating journey times at the very least.
When the Psion 5 came out, the only mapping software was En Route, the forerunner of TomTom. I gave up on this as its mapping was out of date and didn't have the junction of the newly-opened A14 with the M1/M6, which is rather essential to me.
Later, when I updated my PDA (remember them!?) to a PocketPC-based HP Jornada, I gave what was now TomTom another go and was very impressed. Although I didn't use it, it did now have a GPS capability (you needed a separate unit) so that you could see when you were on the pre-prepared route. Spoken directions weren't a feature yet, though.
I've also used a couple of versions of AA Milemaster, which had some interesting features, including the opprtunity to include waypoints and stops, as well as some of the first street-level mapping. It's main downside, though, was that it twice sent me in completely the wrong direction at roundabouts, a cardinal sin in navigation terms.
One of my tests of navigation devices is to set a route from where I live to Peterborough. A good system will send you down the A14, using major junctions, and then up the A1. Poorer ones turn off down very minor roads to cut off a corner (they can't tell that a dual carriageway is faster than a single-track lane) or use unsuitable junctions to join the main road for no discernable reason. Google does this latter, even now.
Consistently, since the PocketPC version, TomTom has used what I'll call the "sensible" route (avoiding the endraringly-named Mad Bridge) and it does this generally. I have it set for the quicket route (a lot of sat nav "blunders" are, I suspect, caused by people setting the shortest option). It does occasionally have trouble distinguishing a minor road from a really minor one, but it's usually obvious when that happens and it's frankly rare. On occasions, if you take its advice in favour of what you think/"know" to be best, it turns out not to be so far off the ball. And, of course, trying to find your way round a strange town, any advice is better than none. Just watch out for No Entries that have sprung up since the map was updated!
Any navigation system is only as good as its mapping and its routing alogrithm, so a bit of planning with an atlas won't go amiss. Nevertheless, following spoken instructions is always going to be safer than trying to consult a paper map and drive at the same time.
