I have a TomTom and I don't know it's the best because I haven't tried other GPS products. I have no problems with TomTom so far.
I drove with some friends from Houston to San Diego about a month ago. We used the Garmin on the drive and all week while I was there just to get around. I haven't used TomTom, but Garmin was awesome.
I got a Navigon a little while ago for like 99 bucks. Its really compact, and I can even walk around with it or go cycling with it. Only problem is the wall mount doesn't seem to working correctly, and it sometimes falls off. One of the hidden benefits of having a GPS is when driving at night on streets or highways that don't have much light, you can tell the curve of the road even before you get there by looking at the GPS screen. Thus it helps you anticipate and prevent driving off the road. I've used it alot when driving at night to Austin.
