I've had a NOKIA armband for a 5800 for sports tracking, and when I got the nexus, I thought of getting a new band to continue my happy tracking.
This band is just ok. The build quality is acceptable.
The size is marginal for me. I am 1,79 and 73Kg, with a slim shape, and the velcro is very marginal. For a smaller arm circumference, I think is too large.
The main problem is the sweat resistance. When I cycle, the case dryes out from the wind. But when I run, it gets very sweaty.
If it is summer time, then things get worse with a short sleeve.
NOKIA's band had a couple of bumps at the back (see image http://www.handyersatzteilshop.de/handy/images/g/tasche-nokia-cp-402-lemongreen.jpg) that elevated the material from the arm, thus keeping the sweat away from the phone.
In this case, the whole case gets sweaty, the material does not keep the sweat out, and the result is a wet phone after a 30 minute training.
I wish I could find a better solution.
I hope this helps you people out there.