I did this (for six months) up until recently (quit my job) and I can say that it's a great means for getting your project started. If you're in a situation where you don't have a lot of money saved up and need a job, nothing beats spending time in the evenings and weekends working on your idea. The only caveat that wasn't really noted by the author is that it's NOT EASY. When all of your time is occupied with work (even if you view your project as fun/something you enjoy, it's still hard work), you can get worn out very easily. Be warned that this requires a lot of dedication and focus (sometimes you skip going out on the weekend to build a new feature). It will suck at times but once you get into a flow, it gets easier. What's more, make sure you explain what you're doing with any significant others (girlfriend, wife, boyfriend, husband) as this will detract a lot of time from your relationship and you'll need support for what you're doing.