I've had it for almost 3 months already, and totally run with it all the time, including in my most recent 5K run. It works well enough to track running information, its not perfect, but its about 95% accurate. The fun part is loading all the information to the nikeplus.com website and seeing your results being animated. It helps out a whole bunch, specially for beginner runners.
I also ended up buying some Nike Air Pegasus + to go with the kit, Before that i had the chip velcroed underneath my shoe laces in a pair of Adidas and that also worked fine.
The only thing i wish it had was a pause tracking feature. This way you could see how many times you paused your work out. I also recommend purchasing one of the training sessions from Itunes, these really help out if you have certain goals.

I agree - I use it because I have it, but I don't think I'll buy another when the battery dies. I pretty know how far my runs are anyway, or I can bike or drive them to measure, and I've found the distance isn't all that consistent, since I also run to a specific heartbeat so humidity and temp can really affect how fast I run. Kind of fun, but not great. I don't bother uploading to the computer, so maybe I am missing out on some inspiration there...

I have had mine for a couple of months and really like it. It is realtively accurate on distance and it is a good motivator for finishing strong.

As long as you run exactly the same way as you did when you calibrate it and you are not running on steep hills it will work pretty well. Otherwise it will give you some really squirrely results. Just remember that if it is accurate up to 10th of a mile then after five miles you are now a whole half mile off.
It was really cool and I'm glad I tried it because I just HAD to see for myself but it is not something that I'm going to replace when it dies.