I did an archive and install on a MBP C2D 2.16Ghz, ATI X1600, 2GB Ram.
A split second after launching the install it occurred to me: Crap, all my preferences, Application Support, Apps, etc will be left behind, and I'll have to manually, tediously copy them over...
To my surprise, EVERYTHING was automagically copied over. The Previous System folder was empty, sans a few sub-folders. My preferences remained intact, from network wireless keys, to disabling the F'ing useless CAPS LOCK KEY.
Everything works great, except Little Snitch, HTTPmail.bundle, Fan Control preference pane. The system is as fast as before, but yet does so much more. Ram usage is surprisingly frugal!
Initial Spotlight indexing had me freaked, as my machine was slow on first reboot. I was like, oh heck. But in spite of the excellent file icon generation, quick look, stacks, etc, it's 'teh snappy'! I may be tripping but Dashboard seems marginally faster at loading widgets, too.
This OS is not one to miss. Most of the changes are under the hood, but very meaningful in day to day use.
Oh and: They FTFF!!!! FTP... wait for it... WORKS!!! And it's fast and doesn't lock up the Finder!! WTF? Is this a Mac?!!
edit: Oh, and, Subversion (svn) seems to be part of the default install. Great! Terminal.app is perfect. Only snag was I had to edit /etc/bashrc to include 'source ~/.bashrc' so my local setting would take effect.
This is the best .0 release of OS X ever. It feels like a .3