Originally Posted by TheSuper
Slashgear review, another very positive one. Overall opinion is this is a winner.
Great review, properly in-depth and thorough, a real credit to them. They went in deep. Loved their wrap up at the end. Basically summed up everything that needs to be said.
HTC One Review  - SlashGear
I haven't read them all, or had the time to pay close attention to the details of every review but the Slashgear review is the first one I've noticed that has tried to identify the remaining storage capacity. We can't create a hard and fast rule because the exact remaining capacity amount will vary for final production units and on a per carrier basis
Here are their findings :
Without a microSD card slot, internal storage becomes all the more important. HTC has sensibly bypassed the 16GB point and instead opted for 32GB and 64GB versions, though the latter will be only available in certain, limited locations. Our 32GB review unit had 25.49GB free out of the box.
32GB formatted (NTFS - flash drive for windows) ≈ 29.7GB
29.7GB - 25.49GB ≈ 4.21GB
64GB formatted (FAT/exFAT - MicroSD card current Android phone) ≈ 59.46
59.46GB - 4.21GB ≈ 55.25GB
Gives us a ballpark of approximately
how much storage capacity will be able to be utilized since there is no MicroSD card capability (shame on you HTC).