The iTunes Match beta opened up to developers yesterday, and in case you were somehow under the impression that it actually offered streaming of music to your iOS device, you're mistaken. Apple has confirmed, because apparently there was confusion, that iTunes Match doesn't stream music. Instead, the $24.99 a year that you will pay for the service means that any music you download from anywhere will get "activated" as purchased in iTunes, and then you can download that music to any iOS device or Mac that you happen to have. That's still an actual file that will need actual space on the hard drive.
Apple says that purchased music can be listened to while it's being downloaded, but it's not like you can have your iPhone full of apps and then still listen to streaming music. In that sense, iTunes Match is more of a sync-ing service than an actual streaming setup.
It's too bad -- I'd much rather have Pandora-like access to my music library from anywhere without having to haul all of those files around on my app-filled iPhone. And while you think that distinction might be the issue of some record company's legal text, it's actually an Apple decision, according to the record companies. Apple apparently wants this music to be tied to iTunes, and thus to actual files on your devices. A streaming service could too easily be brought out to other mediums like browsers (which is where Pandora started, incidentally), and thus separated from Apple devices in general.
That seems sort of selfish on Apple's part -- I would hope the ideal is that I have access to my music on iTunes all the time, not just when I'm on Apple devices. But for now, this is the way it's done. If you pay up for iTunes Match, you still get all of the service's benefits, but you don't get streaming of your files to or from anywhere.
Update: There's some confusion over the word "streaming" here. Streaming, as we're using it, means listening to music without actually downloading it on to your device. This is possible on a Mac with iTunes using the new iTunes Match service (just like it is while sharing a library on Wi-Fi). But it is not possible on an iOS device, even with iTunes Match -- you must download the song to listen to it. You can listen to it while it's downloading, but there will be a file that will take up space on your iOS device.