The Garmin C510 Deluxe is easy to use, robust, no problem during 3 years with it in France. The design isn't the best but a good choice overall.

My Garmin C510 Deluxe is fairly accurate if you know the postcode but have noticed it in some cities it gets confused with new inner roads etc. Has been very good in Spain too. Wouldn't be without mine - just about to order another one for the other half!

The Garmin C510 Deluxe is potentially a good product let down by poor ergonomics of software design.

As a UK based station the Garmin C510 Deluxe is very good.
The non-existent instructions do not do credit to the product.
In the UK I have found the product easy to use and accurate - if you cannot find an address try only using part of it or just the post code - I have found that in some instances a full address is not recognised but parts are.
I would recommend the product as the base model (not deluxe) - it is not worth paying the extra for the European maps as the French ones are of no use. (I don't know about others)