This seems interesting. Are you consuming data directly through CKAN APIs or what? I work a lot with both CKAN and Socrata APIs. I'm curious what niche you're trying to fill: is it a one-stop-shop for open data?
We found the APIs a bit slow when dataset is large, so for now we download the file in any format and upload it with our tool. We have another service that sells business listing (bizrake.com), regular folks have hard time dealing with large dataset, so we are building a service where people can search and download specific data.