If you're referring to the leaked updates, then it the information is sporadic at best.
The leaked updates have, in various forms, updated the kernel, baseband (radio), Webtop and the system software. Many people have reported improvements in such things as battery life, camera usage (though very slight) and other aspects of the phone.
Still others, though, have reported that things have either not changed or gotten worse.
As for actual changelogs of the updates, since they are leaked, we can only go by what we physically see, and no one has really compiled a full changelog as to what has actually changed.