Depends on what you want to use it for. If it'* going to be strictly for driving instructions, get something like WillWren got. If you plan on doing some hiking, camping, geocaching, etc., you might want to consider something a little more utilitarian and portable like, say a Garmin Rino or GPSMap 60. These will still do street navigation (they won't talk to you), but the screens are typically smaller. They're great for geocaching! If you don't know what that is, google it.
Also keep in mind that you'll likely have to buy the mapping software too, regardless of which unit you purchase. This tends to add significantly to your cost. By the time I was done I probably spent about $500 on a GPS, software, and a couple accessories (I got a multi-purpose GPS - GPSMap 60CSx). Mrs SSEM has since become a geocache junkie.