OS X Lion - System Requirements

Question

Hi everyone,
Not too sure if some devvs would be willing to 'bend the rules' of their NDA with Apple, but I am curious as to what the System Requirements are for INSTALLING Lion.
I know I can read all of Apple's lovely marketing and PR pages that tell me:
Lion requires an Intel-based Mac with a Core 2 Duo, i3, i5, i7 or Xeon processor and 2GB of RAM. The Lion upgrade can be installed on all your authorized personal Macs.
but I would like to know the specifics as to what happens or is needed when you install it - i.e.
Requirement
Details
Install Space
X.XX GB to download?
Free Space
X.XX GB Available
Disk Requirements
HFS+ Partition, HFS+ Recovery Partition
Recovery Partition
X.XX MB/GB ?
In the event of failure...
... downgrade, insert disc...
I am really looking forward to getting Lion Day-1 but am a little cautious as to how 'nanny-like' Apple is being on the whole issue.
Many thanks!
-AllSeeingMac

Answer 1

4 GB to download.
With any installer, anticipate up to as much as as twice the space to expand (based on past experience), and 15% of the hard drive (an arbitrary number that in all past Mac OS X versions has been the break even point where the operating system does not slow down) to be free for a full installation.
To downgrade, restore your backup.  You did backup your data?*:
http://www.macmaps.com/backup.html
Note, it will ONLY be available on the Mac App Store, unless enough people give feedback here: http://www.apple.com/feedback/macosx.html This says you'll want to apply the 10.6.6, 10.6.7, or 10.6.8 combo update to install it first on top of an already installed Snow Leopard system if none of those three operating systems is already installed. Snow Leopard will upgrade an existing Tiger or Leopard Intel CoreSolo or higher system system.  So get it while you can, or deal with the sometimes less than reputable used or refurbished Mac shops.  Only Lion will require a Core2Duo, Xeon, or higher system.
Reasons why other distribution methods than the Mac App Store are preferable:
1. In event Apple does not offer a means of making a portable installer which can be used on from any Flash or DVD drive, you'll have to download it for each machine at your internet speed. Also, you'll have to ensure your Snow Leopard CD never wears out (practically impossible),and you keep a copy of the combo update on your backups.  Erase and installs will not be practical.  Your internet connection, and Apple's server will have to have uptime anytime you need to restore it.
2. In event Apple does, a 5 Mbps connection is what is needed to download the installer in 2 hours, let alone additional installion times.
3. Apple did announce at the developer conference the Mac App Store is now more successful at sales than Best Buy or Amazon, or anyone else.  Even so, the last mile has yet to be reached, and goodness knows how long Snow Leopard will be available in retail channels.
Apple has not yet announced backup partition requirements.  Nobody yet knows if their software will or won't be compatible.  You can start by verifying that all your software at least is Universal or Intel, since the net has been humming that PowerPC support may finally be gone, and Rosetta won't be there.  Since Apple hasn't announced the truth of this or not, that's another thing to ask in the feedback link above to ensure that PowerPC support remains.  Quicken 2007 and Appleworks have few comparable alternatives for people to upgrade to.   And Apple has always made Macs run a minimum Mac OS, the one that is presently available new, and none of the older Mac OS  (i.e. if you buy a Mac new after Lion's release, it won't be able to run Snow Leopard).  This past history has left a lot of concern.