You're able to disable Flash on Android by default and only load it on a site when you approve it. It doesn't 'ruin' anything at all, because you'll never be using it unless there's Flash content you want to view.

Having content on the web that's unviewable to a device does more to ruin the experience than a performance hit while doing something CPU-intensive.

Also, from what I've read, this beta of Flash doesn't make use of any hardware acceleration, while the final release will.