I got a Viamichelin x970 from pixmania.ie, who seem to have a pretty good range of devices, and often has a couple on discount.
It has worked out well, though some of the features are not very good, e.g. it has a bluetooth hands free feature but you really need to shout into it to have anyone you are calling hear you.
The menu structure takes some getting used to as well, but on the whole I have enjoyed using it, and have been taken on routes I never would have known were there to get from A to B.
One thing though, and I'm not sure if it applies to other GPS units, is the due to the fact that Ireland has no postcodes you can be driven demented trying to find somewhere by entering a street name. For example, the machine seems to think that anywhere in North Dublin is in Swords. As a result you need to point to where you want to go on a map. This issue doesn't happen in countries with proper post codes, so I can't blame the product.