The current Ubuntu development cycle no longer has Alpha releases. That's supposed to be good for the developers since they have less frequent interruptions and can therefore concentrate on getting the goodies to us users faster.
Unfortunately, it also means people who like to try things out at regular checkpoints will have a harder time. Since there's no fixed milestone to check out on Ubuntu's progress, the only way left would be the daily builds.
That's not really a bad thing, I suppose, since Ubuntu's daily images have been pretty solid in recent cycles. Another way to keep tabs on Ubuntu's progress would be the status page.
The downside of the status page is, of course, the simple fact you can't experience what's going on in Ubuntu. It's just a bunch of numbers. To get the experience, you'll want to give the daily builds a go.
This early in the cycle, though, don't expect to see much. We just "know" stuff that's pretty much standard fare. Kernel 3.8 is expected to be Ubuntu 13.04's kernel, Gnome won't get updated this time, Ubuntu is focusing more and more on mobile... stuff like that.