Just be careful with the screens on Navman units.
I've witnessed a couple of failures recently, fairly early on after purchase. The problem was not with the screen failing per se (could happen on any LCD display unit), more with Navman's complete lack of customer service, and absolute lack of intent to honour their warranty.
In both cases they tried to claim it was user abuse. The first unit was 4 months old, but in pristine condition. The second was brand new out of the box, failed on first usage. So where exactly was the abuse they claimed?
All attempts at reasonable dialogue with them were refused, persisting with their claims that it was user damage.
In the case of the 2nd unit, they only repaired it after an independant assessment and threat of a lawsuit. The owner of the 1st unit gave up in the end, but PC World (the retailer they'd bought from) were good enough to do a substantial chunk of goodwill on a new TomTom unit for them.
I wouldn't say that the TomTom was any better in terms of reliability, but at least they sort it out with minimal hassle when it does go wrong!