Jenma- i haven't really found any cons yet with the nike+... Here's what I love so far about it:
1) The shoe sensor is small so I don't even notice it (don't have nike shoes, just bought a little pouch made for it to slip over the laces)
2) I can check my pace, distance, time, calories burned at any time by the push of a button
3) I can choose whether I want to run to music, podcast, radio or no sound
4) You can set workouts to be open-ended (basic) or to end based on distance, time, or calories burned
4) After your workout, you can set it to sync to the nikeplus website automatically and it saves all of your runs
5) On nikeplus.com you can set training goals, challenge friends, or join virtual races then report your progress
I'm still getting used to running with headphones in. My neighborhood is so active that no matter what time I run, I'm always passing people and saying Hi and whatnot. Just this morning I saw my daughter's friend's mom out for her walk, so I yanked out the headphones to say hello. That's not really a nikeplus thing though! Maybe one downside is that you have to have either and iphone, and ipod touch 2G, or an ipod nano. If you have the nano (like me) then you have to buy a sport kit which includes a receiver that plugs into the base of the ipod. This might affect how some cases or armbands fit, but they do make special ones to fit it with the receiver in place. I just run with it in my hand right now because I'm doing these intervals. I am thinking that when I get to the point I'm running for extended times, I will probably buy an armband. Oh the other thing is that you can't replace the battery in the sensor, you just have to buy a new one. But nike claims that it lasts for about 1000 hours.