I've also noticed that my Macbook Pro boot sequence only occasionally ups the brightness to full when rebooting. (However, I reboot so rarely that I don't really mind.) I thought it was just me! I'm running OSX Lion (10.7.4), btw.
I like the suggested answer that the user preference value isn't read soon enough, but I suspect that the issue is that the appropriate driver isn't loaded until the last moment. From what I understand, the user prefs would be readable at any time during the boot sequence (assuming the root/boot disk volume is mounted, anyway), but if the driver isn't loaded, the value wouldn't be applied. That would account for the display being really bright for some time, but it doesn't explain the occasional (for me, about every second bootup) dimmer value.
Of course, if the dimmer code is part of the BIOS, that's completely wrong, and it probably would be down to when the user prefs were read and fed to the driver!
The strange unpredictable behaviour may depend on what sequence of events occurs when shutting down; it's possible (though not probable) that in some situations, the brightness register isn't reset when shutting down. This probably wouldn't happen if the machine was off for some hours/days/weeks. It would be interesting to see if there's a pattern to the behaviour though!
It might be possible to re-order the sequence so that the display brightness setting is applied sooner rather than later, but it will still be some number of clock cycles between the LED backlight being turned on and the appropriate driver load/preference read.
Apple has a very nice explanation of how Migration Assistant works, what steps and accessories you need and much more:
In a nutshell, Migration Assistant has three bins of data to move:
- Applications (just the programs - no user data or settings transfer)
- Users (the user data, settings, preferences, saved files and such - but no Applications. You could have all your Word docs, but no Word to edit them in this case)
- Everything else that's not an App or a User. This gets oddball things like /Users/Shared files and folders that don't belong to one user, unix and command line tools like homebrew that get installed outside /Applications and /Users.
So with three check marks (let's assume you don't have multiple users), there are 7 combinations you could migrate - each leaving a different set of data on the destination Mac. (If Applications was A, Users was B, and Everything else C) You could combine them as follows: A, B, C, A+B, B+C, A+C, or A+B+C
I would say, you get to experiment when you get your new Mac. Run the migration you think is best, and then test it. If you don't like it, erase the destination Mac (booting into recovery mode, erasing the HD and re-install a clean OS might take 25 minutes on a fast network - the OS download is 4 Gb or so) and re-run the assistant.
For me, I would recommend both migrating from your Backup and then optionally re-migrating from the old Mac. It's important to test your backup - when was the last time you tested a restore to be sure you have a viable backup?
Everyone says "make sure you back up" but they really mean and might be better saying is, "make sure you can restore your backup and it has what you need!"
I would encourage you to configure your Time Machine on the old Mac to exclude any things you don't want moved to the new Mac, make a back up and write down the time of the back up. Then eject the backup drive and change the backup settings to back everything up again.
You could take that "latest" backup and Migrate it to the new Mac and test for a while (re-connecting the backup drive to the old Mac) to keep your "main" Mac backing up.
As you test the new mac for a day or so, you can decide it's time to move over. At that point, turn off Time Machine on the old Mac and connect the backup drive to the new Mac. It will offer to "inherit" the old backups and you can move forward. Worst case, you still have the backups to restore something needed and then can clear the old Mac for donation, sale or mothballing.
Best Answer
Usually when migrating to a new computer whether it is with migration assistent or other software, it will always cause your hard drive to be fragmented which will cause your computer to run slow. In some cases it can be very fragmented. I would recommend running DiskWarrior this utility is incredible how much faster it can make a computer, especially after migrating to a new computer. P.S. in the future I would recommend using Carbon Copy Cloner for all of your migrating, it is a lot easier and safer way to migrate.