I really like the systems based organization of Step Up, which is a big plus, but my one big complaint is its scarcity of detail on many topics compared to First Aid (generally considered the gold standard). It does contain a lot more charts and graphical representations, though. And these are great for comparing and contrasting diseases and syndromes and for getting visual representations of concepts.
I wonder why the First Aid folks don't offer a version of their book arranged in systems format. (There's a systems index on the inside cover of the 2003 and 2004 editions, but it's just a band-aid. The basic framework is still subject based.) I suppose they don't have much motivation to do so. Nearly every med student that I know ends up getting it.