I'm using it. I saw a review about it here on WPCentral and tried it. I really like it. There are some nice pictures posted on there. I'm trying to get my wife to download it on her iphone.
There are a lot of neat pictures from other countries on there. I'd like to hear from someone that uses instagram to give a comparison of the two apps.
I've been using EyeEm a few days now and I'm really enjoying it. Well I just put it on my droid and its even nicer. Seems to be much more advanced. Hopefully the WP app will catch up.
I'm using it but just for the filters. Haven't really used it to share my pics or anything. I've tried a bunch of apps and its got the best filters so far