Globalpositioningsystems are Ok, I've bought two Mio 168's from them. Mine running TomTom Navigator 3, and a year later one for my Son with Tomtom navigator 5.
First question - do you want a PDA or a dedicated SatNav? PDA's obviously have other capabilities.
Second - what software? This is tricky, as there are loads to choose from, and they are all a little different. Recommend some research on the pocketgps forum. This is the GPS equivalent of Pixalo - well worth a visit. Personally, I like the TomTom. for instance, when I was researching, and it might have changed now, Co-Pilot required a complete reload of the maps etc if you wanted to update the safety camera database, whereas Tomtom do not, so is much quicker to update.
Maps. Unless you are intending to use it on the continent, the basic package, Britain (can't remember if they still include major European roads in this package) is probably the best value. You can add other maps later if needed.
Third, if you have a windscreen that has demister/sun screen technology, the GPS signal can be blocked. You might find you will have to use the 'exterior' aerial. This can be effective mounted on the dashboard near a corner of the screen, or by a side window, or even the rear screen with an extension.
You can get good offers from unlikely places like Lidl. These are usually clones of the Mio or others, but the software is maybe not as good as the mianstream ones.
Dedicated units that I would consider are the TomTom 1 or 510. The Mio has a built-in GPS receiver, whereas the HP and other pocket PC's and PDA's used to need a GPS mount, or other GPS hardware to work with SatNav. This might have changed since I was looking at the various systems. I think the software is the most improtant element.
I could go on forever. This is a big subject. Don't rush into it, do the resaerch. What is good for me may not suit you. Now I sound like the Godfather!!
