I just updated. I now have 11:05 hours. Pretty good I'd say. late 2011 15" i7
Here's how I update my mac:
I make a bootable usb flash stick that has 10.8.2 on it.
There's lots of instructions out there to guide you through it.
It all starts with bypassing the updates in the App store.
From there download 10.8.2 no update here, full install.
Search online for detailed instructions, it's super simple.
Start by mounting a disk image "InstallESD.dmg) located within the mountain lion install app.
Then, using disk utility, restore your usb stick to the mountain lion "InstallESD" disk you've just mounted.
Then wait.
Once done, eject usb stick, shutdown mac.
With usb stick in your mac, boot while holding down the option key.
Choose your usb stick (That has 10.8.2 on it) and install.
All your information and data will be untouched.
I think doing it this way is better that updating, check out my batter life.
The ultimate, as many know, is to timemachine backup, wipe your drive using disk utility, boot from usb and install on a complete clean drive. Mmmmmm.... I think that's how apples grow best.
It's too bad that mac need such care when installing os but from what I've read, the above method works. Again, my mac went from 8.5 hrs. with 10.8, then 9.5 hrs. with 10.8.1, now 11:05 hours. Not bad Apple. It's too bad that mac need such care when updating but I think the extra effort is worth it. If anything goes wrong with your mac and your wifi isn't working, you now have a bootable os from your usb.