How much media do you folks carry with you? With Cloud computing coming all of your Media will be stored with Apple pretty soon, right? Is anyone really carrying around an external drive as opposed to swapping at home before a trip to have the right media on hand?
If you use your laptop for syncing your iPhone, and you download a bunch of podcasts, and you have a reasonable library of books, you can easily get to 100 gigs+ after a year assuming you have like Offica, and a collection of other software on your machine and a couple of games. 100 Gigs is pretty easy to get to, and when you do it borks your machine. 256 gigs IS much harder to get to and keeps you from having to pay attention to this, and it always comes up when you least need it to. This is even with cloud storage, which doesn't delete or change your local storage at all.
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I have a 2011 27" iMac and plan to use it as a Thunderbolt display as needed for the Air, but mostly I will use the Air in classes to follow powerpoint/keynote presentations, take notes, read textbooks on the Nook Study app, and some word processing, spreadsheet, web, and mail usage. I don't really see the need for the i7 except that I have a quad core iMac so I am used to the power. But my 2008 MacBook is a 2.4 Core 2 Duo I think. For me you can almost never have enough RAM. As for storage, I don't really plan to have anything on this drive. OS, some books, some docs, etc. No media. I use an external 2TB drive for iTunes on my iMac. No movies, etc.
If you haven't used an Air, you're in for a pleasant surprise. It is MUCH faster for most stuff all the time than your beefier machines like your desktop. Stuff just feels more well oiled and responsive.
Games bad. Massive CPU projects not so good. Plain old computer stuff... Beauty!