I honestly think Lion and now ML are the worst iterations of OS X to date. Mind you, I've been using Macs since and LC with OS 7. The greyscale icons, the lack of any color in the menu bars or Finder sidebar seems to me like a huge step backwards, not to mention simply boring. At the very least, let ME decide whether to have color or not in a preference tab that should be integrated into a single pref pane. Also, the Documents folder lacked the ability to sort by clicking at the top. Stupid UI features carry over, like the Finder prefs and View options. iCloud offers me nothing I really need and i resent Apple requiring Lion or ML in order to use iCloud and basic features like Back to my Mac. I used that feature in SL to support various relatives Mac's scattered across the US. Most of SL and one has Lion. There is no technical reason for this, just a marketing push by Apple. The one other MobileMe ( .Mac) feature I used was iDisk, thats gone now too.
I upgraded on the first day and today, I went back to Snow Leopard, which will likely be considered the last of a fine breed. My MBP and 27" i5 iMac with ML became slow, lots of spinning beach balls and both had Wifi issues that didn't exist before. I don't like Safari's integrated address and search field nor its sluggishness and total failure to load some sites. The new Safari is a weak attempt by Apple and doesnt really compare with more robust browsers like FF and Chrome.
Overall, the OS was not impressive and offered me no functionality enhancements that I needed. I'm back to Snow Leopard and probably here to stay.