Regarding CD's - of course you won't be able to burn the AM content to audio CD's - those are DRM free - allowing you to play them in any player.
For those (like me) that are iTunes Match subscribers who opt in for the AM trial, you need to know that you can't opt out - you're "stuck" with AM until Sept 30th. I say "stuck" as the one restriction I found intolerable was the single session limit for a single user subscription (eg. mac mini playing iTunes Radio in living room and Apple TV upstairs also playing iTunes Radio at the same time). Under Match I was only limited by the number of devices. Under AM, I'm limited to a single session. Kicking off another one kicks the prior one out.
You get around this by changing your "trial" to a family plan, then disable auto-renew, so you aren't billed come October 1st. (unless you think it's worth $15 a month that is).
The whole point of AM is to make buying music pointless. Why would you buy it if it's in the AM library???
The fact that some content isn't in the AM library seems a bit like a bait and switch on Apple's part - I think most of us assumed that AM would have the entire iTunes library available.
And for those that don't understand the point of iTunes Match (there were a few posts earlier in the thread) - I don't have to have any of my music on my phone. Stream all of it, never hit my monthly cellular data usage cap. My next phone will be the smallest amount of storage that they have available, as I don't need much for apps. I'd rather keep my data in the cloud and stream it.