I've been using my nano with Nike+ for a month now. I think Nike+ is very good. Distance is usually accurate to about 0.1/0.2 of a mile (I check afterwards on mapometer) and there is good info on pace and mile times. Some good motivational stuff too - I loved having Paula Radcliffe congratulate me after my last run!!
The ipod itself is great and I particularly like having the radio - I was laughing at Graham Norton while running, must have looked a bit insane!
The only drawback for me is that you can't (as far as I can see) pre-program a workout with timed beeps for doing intervals, so if that's something you need then a GPS or sports watch would be better.
i want a new ipod as my shuffle has just broken. was considering the nano for the Nike+. i used to use the Nike+ wristband and shoe chip thing but gave up after a while as i just couldn't get it very accurate and ended up just using it as a watch
is the nano worth the extra money just for the Nike+? I can't decide whether to get this and give the Nike+ another go, or just get a shuffle for £40 and get a garmin maybe at xmas for the times/distances