I've had a read through of Other Worlds, and in some ways I like what I see and in some ways I don't. There's a lot to this book, and I think it is well written and explained. I'm just not quite so sure that Mark managed to achieve the rules light system he was after.
I find the chapter on world building great, and I love the idea of the GM and the players getting together and building their world together with equal input. Very nice idea that has been bandied around a bit, but this is the first time I've seen it laid out in black and white.
The character generation system is in it's own way innovative, and I like what it is to a point. The establishment of templates is a great idea, which creates a lot of freedom but I feel potential limits character generation to a degree as well. All templates follow the same patter of 8 skills, 4 traits, 4 relationships, 4 goals, 4 flaws. Granted you don't have to take all that's offered, but removing any of the template "bits" doesn't allow you to add anything in it's place. Each character gets 3 templates; cultural, professional, and an Individuality template which is designed purely by the player. Trademarks are added, which are just another template following the same design as all the others but can represent things like gadgets, powers, pets, race, etc.
Games can be set at various power levels from neophytes to god-like beings, which makes sense for a game that can be used to play the Famous 5 or the Justice League. This is a great touch, but really not much different to what many universal systems try to achieve. I think Other Worlds does this well though.
The system itself is a fairly easy to learn percentile system, modified by the game's power level and a character's abilities. Easy to learn and simple to apply.
NPCs are often just simplified characters with fewer templates. I like the idea of simple NPCs, so it gets a big tick for that.
There is lots of GM advice on how to run an Other Worlds game, but I find the advice useful for just about any game, and well worth the read. I don't think that any GM can say that they can't improve their skills in some manner, and this section does a good job of providing a great toolkit.
I have to say the character sheet is just plain ugly, and looks confusing to read. Not sure how it would work in a game, but I can see players desperately trying to find their skills and abilities which are scattered all over the sheet.
Overall, I give the game 3 and a half dice out of 5. I like it, but I'm not sure I would play it.