I've had a Garmin Nuvi 255W for a couple of years and very pleased with it. Maps cover Western Europe - I've used it in the UK, France and Spain and no problems. The traffic alerts depend on what's being broadcast so can be a bit variable. On the Garmin, you need to have the power lead plugged in (and another little wire aerial that plugs into it) to get the traffic function.
It shows a little red/green/amber traffc alert with the estimated delay. You can then look at the map to see exactly where the problem is. It will try and re-route you if there are major delays (e.g. it was desperate to get me off the A27 when going from So'ton to Brighton when the Goodwood festival was on). However, one time in France there were roadworks with delays, but no mention of it on the satnav.
I think it's easy to use. There's probably a more up to date version now, but I'm very happy with the 255W. As a newcomer to satnav, I was delighted with the functions like find the nearest ATM, fast food outlet, etc.