I have invested in one deal so far (https://www.nextseed.com/offerings/rambler/) and my returns have been about 12% annualized which is what I expected from my loan. I think it's cool to invest in local businesses because you can potentially see the growth of the business in person.
When you loan money to businesses on NextSeed you also get perks at the business such as free food if it's a restaurant. In that sense it's kind of like a combination of p2p lending and Kickstarter.
I'm probably going to keep using NextSeed if I see deals in my area. I wish they had an auto-invest feature. The platform is still very new and there are not a ton of deals available but I think it's very promising.