Personally, I use it mainly for driving and on occasion for walking. I've used it once or twice to find local venues, though I've typically used my FourSquare client more for that.

The key things I use it for is getting from once place to another while driving. Often I use it for night driving, even when I know the route, since I tend to drive/navigate by landmark. Night driving is difficult for me, since I tend to miss turns when I can't see my cue, especially in rural areas. Nothing alerts you to having missed a turn better than "Robo" shouting "Turn left onto the street you just passed!"

I also have used ModRana for tracking where I've gone via the track logs. It's handy at times to know about what time I was at point X while driving to my destination. That's useful the next time I pass that point, since I can know roughly how far along I am. Often I can look back on track logs to help me figure out if a different route I took was actually slower or faster, or if it just felt like it was. An odometer can tell you how long a path is, but not how fast you traveled along it.

Probably the most "epic" trip I took with it was about 400 miles. It almost made it back in one go, but back then we were still having the redraw induced sgx bug, so it wound up locking up about 20 miles from home.

On thing I do miss right now is the ability to do off-line routing. I know, that's a big thing to do, but it's really the only feature I've missed on those rare occasions when cell service is not available. I'm sure there are plenty I'd love to have that I don't even know about! But then that's harder to miss before you have it.