When I bought my iPad, I was being cautious because I wasn't sure if it would be everything I needed it to be. I bought a 16GB WiFi only. I have owned it for about 5 or 6 months and I have only encountered 1 or 2 instances where not having 3G was painful. Also, I have no issue with the harddrive size. I use dropbox and pogoplug so the space consuming things like music and movies and lists of pdfs are not always directly on my iPad. This isn't a problem for me because most of the places I have been going have wifi that I can access without a fee. As spring approaches, I think it might be nice to take my iPad with me when I travel or just to sit in a park, but I think there's a simple solution to the lack of 3G in my iPad so I can still do these things. My cell phone carrier provides a small card-like portable wifi generator. I can purchase one of these and subscribe for the service during the time frames when I need it, then turn it off and not pay for it during the time frames when I don't. Plus, I am able to use my laptop (which does do more than the iPad at times) on this same card, whereas with the 3G I would not be able to.
So for everyone that thinks bigger is better, you can keep spending your money, but I have access to almost 1 terabyte of music and movies from my iPad with the ability to minimize the cost of subscribing to a wifi provider because I thought outside the box and found alternatives that ended up costing less than the 64GB 3G iPad.