The i3, which apparantly some people have bought for £99 (I've got one) is a superb unit for the money... it's only downsides are
1. The chipset used for the satellite reception is not very sensitive, it will often get a little less accurate, and be a little woolly at navigating when it is 'waiting for more accuracy'.
2. It's refresh is a little slow, you need to keep an eye on the instructions, as it does lag behind a little when in more complex road layouts..
3. You can't enter a destination by a point on the map, which very rarely is necessary if you visit people out in the sticks that don't have house numbers, and there postcodes stretch for 2 miles..
However they have some very good points
1. One of the easiest interfaces to use, despite not being touch screen, the menu system and access to normal navigation features is slick..
2. The maps are really good, very accurate for me at least, and routing is excellent.
3. The speed camera handling is quite intelligent.. it only keeps annoying you whilst driving over the limit..
I gave mine to the missus, and use the TOMTOM one for myself, but I've compared the two on several journeys, the satellite reception in very built up areas is one area the TOMTOM excels, as is the speed when you come upto some complex series of roundabouts.. other then that, I'd say there is little in it for most people...
And for those people looking at the TOMTOM ONE/GO300/GO500..
The big points in favour of the TOMTOM ONE are
1. It uses the new SIRF III gps chipset, much more sensitive, works in all cars, and built up areas with tall buildings (poor view of the sky)
2. The processor is much faster, so refresh speed/lag is superb
3. It's a slimmer unit that is easier to put in the pocket, or hide in a cubbyhole.
It's screen size is the same as the GO range.. it's only the case that's smaller
It has got less battery life then the GO's, due to its smaller dimensions, but over 2 hours is more then most people need, it comes with a car charger which most people would use perminantly...
Speaker quality is not even an issue, it's clear and loud.. louder then you will ever need..