How is the experience of using Block.io as Bitcoin wallet? How is their API?

Update

Found the following info about Block.io...

1. https://en.bitcoinwiki.org/wiki/Block.io

2. https://www.reddit.com/r/Bitcoin/comments/2dz8rz/introducing_blockio_the_zero_tx_fee_api_wallet/

3. https://twitter.com/anazir