I've used GadgetFlow service to promote my new product – www.challky.com. I've used their Premium plan which included a whole bunch of this such as a daily newsletter, weekly newsletter, mention on all of their social media profiles, permanent placement on their website etc.
It is quite hard to calculate the whole effect of this campaign because the day after they posted our T-shirts on their website and sent out a Newsletter to their subscribers we had a lot of exposure on the Internet and the traffic came from all over the Internet and countries we even never heard of... Thus, with The Gadget Flow you not only get a direct exposure to their huge community but you'll also likely to receive a lot of exposure from other blogs who are following The Gadget Flow and reposting interesting products from their website to their own blogs.
I would definitely recommend using The Gadget Flow to anyone who needs to get a lot of Internet exposure and traffic in a very short amount of time. Yes, the price for their services isn't cheap, but the results we gained far outweigh the cost.
P.S The team at The Gadget Flow is super helpful and friendly too