I picked up my GPS just a few weeks before the MOA rally, this year. It has paid for itself a number of time, already.
For one, it was GREAT having a prompt come up on screen to tell me where to go. A LOT easier in heavy Montreal traffic than trying to look at a map.
Second, I left a concert on Friday night, and was jammed into traffic. I ended up making a big loop on some very minor roads. The GPS told me how to get to the highway, and I saved a ton of time. If you've ever been to something at the Palace of Auburn Hills, you know what I mean. I've also used it a number of times to "route home" when I've been out riding, and want the fastest route back.
Third, it's nice being able to see where I've ridden - mine has a nice track log.
I can't see being without it, now!