Overall, yes I am happy with Mountain Lion. If I had to rate it I'd probably give it a solid 7/10.
Things I am happy with:
- Lovely smooth animations.
- Launchpad is fantastic.
- Mission control isn't as bad as I thought, since you can tweak expose.
- Love full screen apps!
- New dock is fantastic.
- The reminders app is very handy.
- The iCloud connectivity is so seamless, can't imagine being without it now!
- Notification centre shows good potential.
- Safari 6 is Awesome, with a capital A. That's how awesome it is.
Thing I am not happy with:
- The new calendar app looks hideous.
- iMessage is far from perfect, conversations should be merged to one user if they have an email and number under the same contact. Right now we have two separate conversations for the same person, not great. My phone also beeps off the hook when I'm conversing on my Mac, it should know I am talking on my Mac and shouldn't notify me on the phone.
- Mail seems to forget passwords sometimes which is annoying.
- Notification centre needs to be a lot more responsive.
- The App store still looks bad, it needs a new aesthetic. It looks like website.
- Quicktime seems to have become more laggy, adjusting volume during playback results in stuttering.
Thing I am REALLY not happy with:
- iPhoto is still SO slow, please fix this terrible performance!
- I know you need to sell new macs Apple, but stopping every pre-2011 mac from using Airplay was a cheap move.
- My mac has experienced a buggy crash since upgrading, and a lot of people seem to be experiencing this.