1. Threadbare Content
FPWW is a game that emphasises the idea of creating your own fun. You'll primarily do this through the ridiculously deep, complex customisation options and gameplay mechanics, and while this minimalist approach works to an extent (and is likely exactly what series purists wanted from the latest incarnation), it's easy to see why newcomers might feel a tad underwhelmed.
The possibilities within Fire Pro's limited game modes are huge, but the release itself is low on built-in content. There are, of course, exhibition matches, but only a handful of different stipulations (the Landmine Deathmatch is bags of fun though). Fighting Road allows you to experience FPWW like an RPG, Mission Mode runs you through the basics, and there's online play too... but that's about the extent of it.
Though this complaint is wholly subjective, World's lack of accessibility is a concern. It's easy to imagine new players losing interest before ever truly letting themselves get sucked into the awesome gameplay. That's a shame, and while Spike Chunsoft shouldn't necessarily add dozens of bells and whistles to appease those whose gaming diets consist entirely of empty calories, a few extra modes would have broadened the game's appeal.