I'm running beta2 and testing it: and generally liking it. I've reported a couple of minor bugs or possible bugs today.

There's no doubt that beta1 and beta2 are much more stable than the equivalent releases were on 9.3 (until beta3 9.3 was very flaky). Of course on 9.3 the beta was closed - now it's open. I don't claim that the openness has led to massive reporting of bugs and hence improvement (yet... - and it can't have done for beta1). But it has almost certainly had an effect on the psychology of the people working on it, which is an important part of the open source effect. If you know that everyone can see what you're doing, you're more likely to do it well. Which is one reason why openSUSE and an open beta program are a good idea.