Ol' Hankerin has created a masterpiece. The rules are simple to grasp, and very clearly state that if a situation isn't covered by the rules, the best thing you can do is be honest with the players and do whatever comes across as the most fun for the table. The system of a class being based of loot instead of inane abilities means that you can drastically change your play style on the fly with the right gear, or really terrify those players as a DM when they get captured and their stuff is taken. The challenge rating applying to a room as a whole allows the DM more freedom to think on the fly and run a fluid game, rather than suddenly having to pull an arbitrary difficulty number for an unexpected challenge.
I also own the Worlds book, as well as the cards volumes 1-3. The art style is both wonderful and whimsical, and comes across as nothing short of unique and fun. No other RPG to my knowledge is going to have an art style that feels as aesthetically pleasing as an inked noir comic. The worlds book is filled with interesting content, campaigns and ideas. There are also classes specifically tailored to those worlds! (Looking at you Ghost Mountain!)
In short, I cannot recommend this system enough. If you feel bogged down by prior systems being too heavy on specific rules for situations that may never happen (GURPS 4e), or feel that your combat system doesn't strike the fear of death into the hearts of your players (D&D 5e), then ICRPG 2nd edition will be a breath of fresh air into you. No longer will you need to sit there wondering if it really matters that Orc #4 has 18 hit points as opposed to the others at 15. When your players are fighting 1 heart monsters, and that bad mamma-jamma shows up with 2 hearts, your players will know things just got real.