I started on CLO level two while I was taking a college semester of chinese. In my second semester, I finished level two. Since then I’ve done level three on my own, and I’m now moving on to level four.
The only other source for Chinese learning that I’ve used consistently since the college classes is the Anki flashcard software. While I was taking the classes I used my class materials to make flash cards, but since then most of the flashcards I’ve made have been based off of CLO lessons.
I did listen to a number of Chinese Pod lessons for a while, but I found that review was difficult because of the lack of repetition across lessons. Chinese Pod has fun lesson topics and animated speakers, but repetition is essential for retention. After a fair amount of time comparing your system with Chinese Pod, I’ve found that CLO is significantly more effective because of the re-use of vocabulary.
The increase in difficulty has been fine for me. The only part I’ve been lagging on is my study of the characters — I only get about 20-30 minutes a day to study while I ride the subway to work, so it’s hard to practice the writing. I’m hoping that by forcing myself to switch to reading all characters, I can speed up that process.