I was asked if I like running with my Nike+ compared to my Garmin so I thought I'd do a full write up about both of them. I have the Garmin 305 and I have run with it for years and I love it. This year my work did a contest and for every 1000 miles we ran/walked we donated a scholarship to kids in Malawi Africa. So I got a Nike+ to be part of the contest and tracked all my miles. Just for the record I was in the top 10 overall on miles and the #1 corporate employee with the most miles. OK back to my comparison...
Accuracy. The garmin gps seems more accurate than the Nike+ since it only uses a pedometer (unless you use your iPhone then it adds gps - but I don't run with my phone). At first my Nike+ was off quite a bit but I have calibrated my Nike+ a few times and it is much better since I did that. I'd say on average it's about 0.1 mile off. When I run on the treadmill my Nike+ is exact with the treadmill so I don't know exactly where the discrepancy is.
Ease of Use. The Nike+ requires two pieces - the foot piece and a piece that goes into my iPod. If you run with your iPhone you don't have to have the 2nd part. I don't run in Nike shoes so I got this little shoe attachment for the pedometer (I hear they have wrist ones too - but I'm not sure how that would work and my foot piece was free from work). I just move it to whatever shoes I'm wearing and I'm good to go. With my garmin I just throw the watch on and off I go. However the watch is very bulky and sometimes it annoys me when I'm running. It also makes it difficult to take off extra layers when it's cold outside. My Nike+ doesn't take any time to locate satellites either.
Post Run Information. I never hook my Garmin up to my computer so this might be an inaccurate comparison. I upload my Nike+ data almost everyday and I can look at my total miles, set goals, look at each miles pace breakdown, put in details about my run (weather, hills, etc). I really like the constant feedback from my Nike+ and the little shout outs it gives me when I hit specific goals (fastest mile, furthest run, you hit 1000 miles, etc). I'm sure the garmin does more of this but it just isn't as convenient to hook up to my computer as my iPod is.
Additional Information. One thing that I've noticed is different running with Nike+ instead of my garmin is that I'm not nearly as OCD about watching every detail during the run. I run and it tells me when I've hit each mile. It counts up to half way then down which I like and other than that I am just running along with my music. I never look at my pace to speed up or slow down. I feel like I can run at a more comfortable pace when I only have my Nike+ on. And I haven't slowed down a bit if anything I'm a bit faster than I was last year (but I don't think that has anything to do with my Nike+). However, that goes both ways. When I'm training hard the Nike+ doesn't push me hard enough or tell me any details so on tempo runs or speed work it doesn't work and I wear my Garmin.
I love that my Nike+ hooks up to my nano and most of the time I just have my music on really softly in 1 ear so I can chat with the girls but I'm so used to have it with me that if I'm struggling on a run or going up a tough hill I can turn up the tunes and push myself.
P.S. I didn't realize how dirty my shoes are. I am so embarrassed :)