I'm not expecting everyone to be happy, but thanks for putting forwards your views everyone.
In short, the open letter addresses the Construct 1.0 issue. To put it very briefly, it can largely be put down to technical issues: we could release "1.0", and due to its poor architecture, it would still be unstable, so we decided the term "1.0" would be misleading. With our greater experience C2 is much better designed, so the same reason should not prevent the "1.0 of C2". And 0.x is such a mess, improving it from where it is would be more effort than starting from scratch.
Also, the 'desktop runtime' would be OpenGL powered, and can probably hit Mac and Windows in one go if it's coded right. Anyone can make an exporter through the open exporter SDK, so there's a valid risk somebody might make a free one, but it takes a lot of in-depth knowledge of Construct and the event system algorithms to make a successful exporter. That puts the Scirra team at a big advantage over everyone else.
OpenGL can do everything the old 0.x runtime did - shaders and all. When a desktop runtime is in the works, there's no reason to believe it'll be any less powerful than the 0.x runtime. In fact, if we're making money from it, we can spend even more time on it and make it even more powerful! That also depends on the pay-what-you-want system and other factors, though.