I never was too much into superhero RPGs until I came to know Mutants & Masterminds. When that game came out translated to portuguese here in Brazil, I bought the books mostly to support the publisher. I was surprised, first to read what I consider the finest RPG translation into portuguese so far, and second, to find the great game system that M&M is.
First off, I simply loved the artwork. The style reminds of recent superhero and action cartoons and my first impression of the game's tone is exactly that: colorful, maybe wacky, fit for one-shot adventures more than long campaigns. The sample villains at the end of the book also sustain this feeling.
The standard method of character creation is through randomization. Personally I have nothing against it, especially for quick games, but when you have randomly selected superpowers, sometimes you end up with really weird combinations. I'll need to try to create a few ones to see what happens. However, there is the option of creating characters using a simple point-buy system for those who prefer it -- for instance, if you already have a superhero concept in mind.
In terms of game rules, ICONS uses a derivative from Fudge/FATE, including the Aspects system. This is an interesting part of FATE which, at the same time, motivates players to add color and detail to their characters, and puts those elements into play. The system used to describe superpowers looks like the one from Mutants and Masterminds, 2nd edition, but more oriented to description than detailed rules. Powers are divided into groups, such as defensive, alteration and control, and more flexible or potentially game-affecting ones are more expensive to get.
Conclusion: from this first quick read of the book, ICONS looks like a well-rounded superhero RPG, lighter on rules than Mutants & Masterminds (which, itself, is lighter than other similar RPGs, in my opinion). As such, it seems particularly suitable for single adventures in a more cartoony mood. I'm thinking about using it for an adventure inspired in the "Freedom Force" computer game. The downside of the book, if any, is that it does not seem to include much of a game setting, instead referring to the "world of superheroes", which will depend on the players' references.