The "difficult part" is figuring out how to use the system or "the tools available". I think of the rule book as a sort of a toolbox and once you figure out how to adapt the tools to the current situation it usually makes perfect sense. But I agree that you need a lot of examples or a lot of experience to make it work well, preferably both.
For an example, this is how I play interviews or sort of 'exams' where PCs try for example to convince a certain character that they are worthy to join their guild or hero band. I have played a few with different groups and they have been a success IMO.
We have one "inquisitor" asking the questions on the other side and the PCs are on the other side, answering. The inquisitor expects the PCs to have a knowledge rating of e.g. 5w of a certain subject (the Abiding Book, Moral Values, Lunar Philosophy, Heortling Mythology, Table Manners or whatever).
So the inquisitor starts with 25 APs and the PCs with the skill level that they will first use in the contest. The PCs can also act as a group with one AP pool and augmenting each other, but I think it's more fun when each PC has a seperate pool.
The inquisitor then starts asking questions. The AP bid reflects the relevance of the question, not so much the difficulty. The GM doesn't have to necessarily come up with exact questions, you could say of course: "Now she wants to see what you know about the early history of Siglat the Good, Founder of the Hrestoli Idealist church of Loskalm" or just "Now she asks you a really tought question about some saint", both would have a bid of, say 8 APs.
If the situation allows the PCs can also follow up on the question, giving bids that reflect how much they want to say about the subject. Depending on the level of success they either point out insightful details or embarrass themself totally, or something in between. The PCs could also play an even more active part, with the inquisitor allowing them more freedom to "present their case". If you play an inquisition where the PCs are chained to the wall this might be a tad more difficult... :)
When the inquisitor is down to 0 AP she is convinced that the PCs are worthy, when a PC or all the PCs are down to 0 AP they're considered unworthy. Depending on the situation the levels of defeat might not have any effect at all, or for example if the inquisitor is down to - 11AP she might get and impairment to her "Doubt Newcomers" skill, just for a short while of course.
Others must have more and better examples of creative uses for ECs, so bring them on :)
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