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IMAC - only when editing photos.
IPad - all the time, it's replaced the MacBooks for browsing, mail, etc.
Macbook Airs - when traveling, I use them on photo shoots away from home.
IPhone 4S - not sure, my wife ordered me one, should be here on the 14th.
 
Well my iPhone 4 is my work device, so factoring the amount of time I spend looking at e-mail on it its:

iPhone 4 - 60%
iPad - 30%
Macbook Pro 10%

Take work e-mail out of the equation and it looks more like:

iPad - 70%
Macbook Pro - 20%
iPhone 4 - 10%
 
I would have to say Ipad is now my the main device when not at work for all my basic computer type useage and socalled dumb cell phone for making calls only
 
iPad 40%
HP touchpad 40-45% (it's a nice device for what I need, though I am using the iPad to write this. My daughter is playing angry birds on the touchpad)
Home computer 15-20%
 
at work: 70% iPhone (mainly listening to podcasts), 30% Mac Mini

at home: 90% iPad, 5% iPhone, 5% MBP
 
iPhone: 35%
MBP: 30%
iPad: 25%
Windows 7 Desktop: 10%

I only play games on the desktop so very little time is spent there.

Though for 7 hours a day I am on my Windows 7 laptop for work. 😛 I didn't count that towards my percentage because that is forced computer time. Hah. 🙂
 
First, my usage changes month-to-month depending on projects. Second, I am slowly transitioning from iPad 1 to Android thinkpad tablet so my usage is changing.

iPhone 4 - 40%
MBP - 30%
iPad 1/Thinkpad tablet - 30%
 
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