I was disappointed by Put.io in the past, it over promised and under delivered. It seemed like an unstable app with very slow speeds. It looks like they have improved since I last used it, I will give it another try.
I used them before and I'm trying them again. They now seem to allow you to pick the best mirror available for you, so your ISP's peering is no longer a problem.
I use http://www.cloudload.com, it is a similar app and works like a charm.