I don't think a single resource will teach you all you need to know about any language, even if this one is pretty good. So by all means pick up a textbook. At the least, you can leaf through it when you're not online.

Taking your question seriously, I think Popup Chinese is best at the elementary and intermediate levels. I don't know if it would be good for learning totally from scratch but I'd guess the toughest thing about learning this way would be getting the confidence in things like pronunciation, etc. since there isn't a single podcast that systematically goes over that.

I remember David mentioning once that they expect it will take people 3 months or so to work their way from the Absolute Beginner content to the Elementary level. This is actually not bad if you consider some of the elementary dialogues. So I don't think two weeks is really much time at all, and certainly not enough to beat yourself up over. What might be helpful is if you could identify the areas where you're having difficulty. Maybe they can put together a couple of lessons to fill in the gaps.