Just upgraded my laptop from Lucid Lynx 10.04 to Maverick 10.10. It was (happily) largely uneventful. One thing that I had to figure out was that Upgrade Manager had been configured to only show long term support (LTS) releases, meaning it wouldn't pop-up the helpful "Upgrade" button. Once I changed "show new distribution releases" to "Normal", it showed the "Upgrade" button and the upgrade proceeded.
One touch I like in the new release is the use of round-er sans-serif fonts everywhere. Feels a bit more inviting than before. Python is 2.6.6 by default with 2.7 and 3.1 available. Unison has been upgraded to 2.32.52 which means that I'll need to upgrade my desktop before I can synchronize again.