well a bit out dated but i do have the HRM with my 6thGen nano and run with it every time i can and remember. the HRM it self i would describe it like a small one size bra strap with a transmitter attached which is the bulkiest part. when the sweat get rolling you know if the Strap is falling so i always run with it snug. kind of annoying but with working out in a building I.E Gym most equipment detects and reads the Sensor so i can use it to my advantage with out a "Click" to tell me pace and rate. a few notes which will conform some things for you guy/gals
1. sports band or 5th gen nano and newer only
2. it will not work with the pedometer function (only Nike+ fitness workouts)
3. every workout after syncing the Hrm will ask you your Heart rate ranges mine are 135 to 190 currently
3a. even if you do not use the HRM it will ask you if one has been linked
4. the nike+ website has a very basic implementation of the HR data hope to see better here sooner or later. (new to slow geek and running)
overall i think it is an ok system but nike needs to revamp it yet again. the system is missing way to much for the newb like me and missing so much more for the avid runner. i looked into adias as well but don't like that system due to its heavy start up price. i already had an ipod so the Nike+ was the easiest to implement.
looking forward to learning the in-s and outs at slowgeek hope to be of help one day.