First, a full-time consultant has to spend time getting work, and he doesn't get to bill that. That's part of why the 2-4 ratio exists. I've heard that you can expect to spend an hour looking for work for every hour that you bill. Also, being a consultant is riskier, not only in the short-term financial sense, but also in the long run: if you're unsuccessful as a freelancer, you've got nothing to show other than the fact that no one wanted to hire you, and you're probably too burned-out/exhausted by searching for work to do any interesting side projects.
I dono... maybe I would have gotten rejected more if I charged more, but I usually enjoy the technical stuff more than the marketing, so it makes sense to work two hours on technical work rather than one hour marketing and one hour technical work, if that is indeed the choice.
I have had the occasional client willing to pay me 4x what I would expect from a salaried gig, but I mostly lucked into those. Some clients offered me more than I was asking, so maybe I would have done OK insisting on the higher rates.
You just have to be careful that you tag things correctly and are honest about it. The default tags and categories are pretty good, but you have to decide for yourself if hacker news is really that productive ;)
I realize how little work I end up getting done, its one of my new years resolutions to be more productive.
And no I'm not organized enough for GTD or what not. Best thing for me has been the joesgoals.com website.
I'd say that I average 45 hours of actual work per week, discounting the time I'm "at work" but goofing off, while including the time I spend working at home, even if that "work" is studying or discussing programming languages with other hackers to trade ideas.
The lines blur some if you are salaried and unlikely to leave your employer or if you are learning things specific to your employers needs.