Made for map lovers, apparently...
The effect is to de-clutter the typical satnav UI, not by removing options, but placing them in a hierarchy of importance. Rather than put up front an icon for, say, looking up POIs, the Start places that icon on the menu you see after you press "Plan Route", on the assumption that you're not going to be looking for places of interest unless you have a journey to make.
The car mount is built-in - but removable
Hitting "Plan Route" calls up the usual screen of departure selection options, followed by a series of screens that let you input that information or take it from existing data - your home, where you're currently parked, a POI - then on to the destination, which you choose in the same way.
The notion is to focus solely on getting from A to B, and this will indeed simplify the satnav process for most people. What it also does is limit browsing: deciding where to go for a weekend drive by looking up interesting POIs first, for example. This is ironic given TomTom's belief that Start will appeal to map buffs, and it's probably why it felt the need to add that "Browse Map" icon to the main screen.
Pressing it calls up a map you can zoom in and out of, scroll around and use to see what's what. It's not a new feature by any means. All satnavs have it, though it's not always brought to the fore the way it is on the Start.
The problem is that a 3.5in touchscreen - and a resistive touchscreen at that - isn't the ideal platform for map browsing. Even if the resolution were a darn sight higher than it is, and the screen capacitive so that taps and drags were immediately interpreted as such and not occasionally the other way round, the Start doesn't provide anything like the same experience you get with a map or mapbook open in front of you.
You can fit it to the dash as well as the windscreen
The screen is just too small. To get a decent bit of map into it, it has to start off zoomed so far out that all the detail is lost. Zoom down to a scale that's relevant to working out where a POI is in relation to somewhere you may be visiting or driving through, and you lose all sense of that location's place in the geography.