Cusith: Its not about billing yourself its about: I'm either fixing a bug or working on my next game or filling out paper work which gets me more money/improves my reputation?
If you can be so efficient with your time and don't ever run out of paperwork to do, sure. I tend to run out of steam after a long day of coding so I can't just work on my project until bedtime. However, I can still squeeze out some time doing other type of things that could net me some money.
Unfortunately, there is a limited supply of such things available to me at any given time. If I could spend my evening sending invoices and making money, I'd do it right now -- much more productive than posting on GOG forums. I'm not successful enough to say no to money. But there's nobody I can send an invoice to right now. I'd take the chance if I had it.
If you (or the dev of the subject) are really in a position where they have the choice to make so much money any time of the day that turning down an easy $140/year is netting you money, my hat's off to you. Congrats. You're probably making more dough than the software engineers in Silicon Valley. I'm a bit jelly ;3
The thing is multiple devs have complained about the billing system GOG use so who knows how bad it is.
Based on what I've heard, the only complaint is that they have to send an invoice instead of automatically receiving the money. Yeah, sucks, I love when everything is automated and I absolutely hate paperwork. But let's not pretend that sending an invoice per month (or 1-2 per year assuming it's ok not to claim your money every month, which is how it should be) is that difficult. I don't believe even GOG can make it that difficult..
Also, regarding reputation.. visibility seems to be a major problem for indie games today, because so damn many of them are released. I don't see how pulling off of a large store is going to help with that. In fact, it might hurt ;P