That's a compelling reason for some users. I thought WA would be slow, and that would be a reason to buy a local version (or a subscription to a faster version)

That's a compelling reason for some users. I thought WA would be slow, and that would be a reason to buy a local version (or a subscription to a faster version), but it surprised me how well it coped with the launch load. But after seeing your freemium idea, I've changed my mind to think they'll just leave off some features - that's the standard approach.