I have had a Dell x51v for a couple of months and for Christmas got an Oncourse BT-339 GPS receiver and iGuidance mapping software. I love this combination of iGuidance and the BT-339 as it has already paid for itself on a trip I was forced to take to D.C. just after Christmas. The iGuidance advantages include lots of POIs, very good and quick routing, low price (~$100), and ease-of-use. The BT-339 is also quick to start, has a 12+ hour battery life and is small and light.
I'm also trying out BeelineGPS and really like it too so far. I've found 2 caches with it already and if I keep this up I will certainly buy a copy before too long.