The standard RPG element of power ups abound. This time in the form of Chaos Eggs you can allocate to your team, giving them attributes like invulnerability or increased ambush moves. The teamwork element is challenging enough and give the game it's longevity, much more so than the combat. But you will end up criss-crossing environments several times as you're always on the lookout to complete the fetch quests.
It's good enough but not great - although if it's a Sonic fix you're after, The Dark Brotherhood will provide it.