The only "advantages" here have nothing to do with wireframing, they're just the advantages of any hosted service. When it comes down to it, Omnigraffle is bett

The only "advantages" here have nothing to do with wireframing, they're just the advantages of any hosted service. When it comes down to it, Omnigraffle is better than Drawings for doing wireframes, because that's what it's meant to do. On the other hand, how about http://www.gomockingbird.com http://www.gomockingbird.com?