You're referring to iTunes Match.
At the moment, it doesn't appear to be an option to anybody outside of the US. But this may (hopefully) change when iOS 5 is released later on today.
Given the choice, I much prefer to actually own the content. Yes, it'll cost me more but I'm ok with that rather than having access to stream songs rather than own the rights to that copy of the song. Funny how things turn around, I do still love Spotify, but I've really been waiting for iTunes in the Cloud for years really so that's my personal preference.