I have Spellslinger and while I have yet to run it, I really love pretty much 95% of it. The only thing I wish is that they would have put a little more details in the background BUT it is ok.
The game only have 3 full-blown classes... the Gunslinger (name says it all, they have the best BAB, has really high hit points and has average saving throws), the Maverik (kind of a rogue/con artist, who has the most skill points, best AC and Initiative bonuses, one good and two poor saving throws), and the Trailbrazer (outdoors guys with some kewl abilities). There are also six ONE level spellcaster classes. Basically you have to take this class at first level and then all spells and spell-like abilities are Feat driving. It is a really cool idea. One thing I REALLY like is that each class as some "core" abilities that you only gain if you take the class at first level, it really helps to make the classes different even with all the multiclassing.