I HAD a TomTom, and would have recommended it until the screen inexplicably broke (while it was in its case). They quoted £30 MORE than the blardy thing cost to repair it . It's gone in the bin, and I won't be buying another one.
we have a tomtom and a garmin - they each have pros and cons. The garmin has traffic alert system which can be useful on motorways but I'd say the mapping was not as good. Having said that, the tomtom does seem not to be able to distinguish a farm track from a real road at times.
Both have been dropped a few times with no ill effects - physically tough enough.
A Garmin nuvi 255w and no I wouldn't recommend it. The map is very out of date (e.g. upgrades on the A1 aren't included, they only update the maps annually) and it just randomly zooms in and out as well as countless other minor annoyances.