I have the RooSport 1.0 and love it for small runs during lunch time where I have to carry my security badge, my locker key, cash, 1-2 gels, credit card, etc.. It's nice, small and comfortable to carry. I have used it twice a week for almost 2 years now and have been happy with it.
For me, it's a little to small for anything more than a training run. I would not want to carry more than about 2 gels in it (but maybe that will change now that it is becoming larger). I also could not see putting my cell phone into it due to the weight and discomfort (but maybe others do not notice).
The magnets are super strong and I have not had any issues with them. The material is nylon and very comfortable. No chaffing or discomfort.
It is not waterproof (but none of my belts are). I always recommend putting all your moisture sensitive items in a zip top bag.
This would be a good product to use while traveling to carry/conceal your valuables and passport. It would also be good for those days where you only need to carry a few items around instead of carrying your whole purse or wallet.
I am excited to see the new/upgraded version being offered on Kickstarter. Go check it out here.
RooSports FAQ will answer most of your questions.