Mine at this moment in time has 8.6GB free. I have:
- 198 apps in total,
- 2352 Songs (18.8GB),
- 55 Videos in Total - Breaking Bad Season 1 and 2, Boardwalk Empire Season 1, A few HD documentaries at 1GB each (12.6GB).
- 801 Hi Res Photos.
- Goodreader that syncs my whole Dropbox to my iPad, (11GB).
- Wiki Offline (3.6GB)
- Games take a large chunk, such as Gangster (2.6GB) Kotor (2.2GB), Call of Duty (1.5GB), Deux Ex (1.5GB) and Fifa (1.3GB).
- Magazines (5GB)
- plus loads of other stuff, Pages, Numbers, Keynote (1GB in total)
Personally I use my iPad alot, it's 80% of my usage. I have my ideas and 'get them down in rough' then the extra 20% is refining and developing on the macbook. So in that sense I see value in going for the 128GB and 64GB (before this one I have now).
There's loads of great tiny apps such as Notability that is only 92MB in size. Netflix is 93MB, Engadget 123MB, Google Earth 70MB, Youtube 60MB. Just to give you examples.
For alot of people the iPad is just a web browser and video streamer, different things for different people!
Edit: These sizes were taken from reading the Usage section of my iPad in the Settings Menu - So are actual sizes, installed on an iPad 4 128GB.