After spending the past hour installing and getting my new Fedora 12 box set up "just right" I noticed that I had around 400MB of updates to install.
With my internet quota almost gone, I was going to put off installing the updates until later that night when I get free data, but decided I should just bite the bullet and go for it anyway. (Australian ISPs have crazy download quotas, if you're not already aware).
I was suprised to see that the package sizes where considerably smaller than they have been in previous releases. Curious, I decided to do some reasearch and found that they now use a different compression type and that deltarpm is enabled by default. Nice work Fedora!
More info at: http://fedoraproject.org/wiki/Fedora_12_Alpha_release_notes#Smaller_Packages