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Save time and just upgrade. No need for clean install, my hard drive space was the dame after or close after upgrading.
 
Thanks Hirakata. Possibly one of the best explanations.

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BTW, I chatted with a rep on Apple.com/store cause I had nothing better to do and this is what he said:

Him: Oh, well if you bought new from us here online, it will come with Mountain Lion 10.8 on it!
Him: Solid, you will have the up do date software on it when you open it up then.
me: the description when I was Checking Out said OS X. It didnt specify Lion or Mtn Lion.
Him: Oh yeah, any bought July 16th or later will have it.

Seems to conflict with what others are saying. Thoughts?

Apple reps and employees are good to a fault. This is incorrect in my recent experience. I purchased a MBA through apple.com on the 18th and it arrived on the 25th. It had 10.7.3 (not 10.7.4) installed. And just yesterday, Apple replaced my 2010 2.93GHz iMac with the latest version (2011 3.4 GHz) because they were unable to fix an issue the 2010 had. The 2011 I took home yesterday had 10.7.3 (not 10.7.4) on it as well. I think buying a Mac around the time a new OS is released is a bit of a crap shoot as to whether you'll get the new OS or the old.

Enjoy your Air!
 
Having upgraded from Snow Leopard -> Lion -> Mountain Lion on my 2010 13" MBA without issues, I don't really see the point in a clean install. Its just a waste of your time having to set it all up over again.

Note I did have some app stuffs that needed updating more so with Snow Leopard -> Lion. Lion -> Mountain Lion had far less app compatibility issues. In any case, you'd have to get updated apps if you did a clean install anyway.

Making a USB bootable drive though for future recovery isn't a bad idea.
 
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