If looking at the 32G version of iPhone is any indication.
Itunes reports available capacity - any user installed data is = to about 29.3G meaning that much of the OS etc is about 3Gig of data.
Sorry, that's actually not how it works
In computing, we use bytes
as a measure of storage (one byte is 8 bits- a bit being symbolically either a 0 or 1).
Because we use powers of two however, 1 kilobyte (KB)= 1024 bytes (2^10 bytes), 1 megabyte (MB) = 1024 kbytes, 1 gigabyte (GB) = 1024 mbytes.
Hence 1 GB = 1024*1024*1024 = 1 073 741 824 bytes.
But in other fields, the prefix 'giga' just means "1 billion"- and that's what all the companies use. Makes sense, it's easier to remember for most people. Plus, that results in a bit more of storage, so it's convenient for them. Computers however consider that 1 GB = 1024 MB.
The 32 GB ipad has 32 billion bytes of storage, but your computer will use the aforementionned method of calculating storage, which results in:
32 000 000 000 / 1 073 741 824 = 29.8 GB.
iTunes shows 29.3 GB available out of these 29.8 GB, hence the OS takes about 0.5 GB, which is 500 MB.
So a 16 GB iPad will have:
16 000 000 000 / 1 073 741 824 = 14.9 GB.
If we substract about 500 MB for the OS (the iPad's OS shouldn't be significantly bigger than the iPhone's/iPod touch's), that's 14.4 GB.
And on a 64GB ipad:
16 000 000 000 / 1 073 741 824 = 59.6 GB, minus 500 MB = 59.1 GB.
Hope that made things a bit more clear
If you want to put 5 movies on it for a road trip with the kids, some books and pictures and podcasts and some audio books and music and don't want to have unload this and reload this, 64 gigs is not enough.
And this is even without any e magazines, e newspapers or whatever someone dreams up in the next 3 years.
I think you're exagerating a bit there. A movie at full iPad res takes about 1.5 GB (I already started encoding my high res movies
So 5 movies = 7.5 GB.
Now if you want to put 150 albums of music, considering 100 MB per album (which would be pretty well encoded music, more often it's about 60 MB per album), that's 15 GB.
Add about 1 GB of podcasts (that's about 15 hours worth of podcasts), and 1 GB of applications (again, an overestimation).
That gives us a total of 7.5 + 15 + 1 + 1 = 24.5 GB taken out of the 64GB iPad's 59.
34.5 GB left, or 40% of the iPad filled up. That's a lot of space left. And e-magazines, etc. won't take that much space compared to a movie, for isntance.
So yes, I think 64GB will definitely be enough for most people.