For a long time, liberals were talking about the sort of things you would actually have to do to get health-care spending under control while conservatives simply criticized the downsides of those intimidating reforms. And the main thing you have to do is get health-care spending into a single budget and then stick to it. You can do that by having the government set payment rates for providers or by having it set subsidies for individuals. Democrats were admitting this and thus taking on the burden of its problems, while Republicans were simply denying it.
Ryan's proposal is an admission of the reality.
Alas, Ryan is hopeless on defense and still hooked on some of the loopier supply-side hooey. But it's a start.