EoFF always makes me feel like I'm the only one who didn't think Kingdom Hearts II was utter trash. I never felt that any of it was especially hard to grasp. I felt that a majority of it was pretty damned predictable (the only exception being (SPOILER)the whole Ansem/Xehanort twist which I really didn't find to be a significant stretch).

As for the handheld titles, I find they're typically more important for linking between the numbered series than anything else. I imagine playing Kingdom Hearts II without having played Chain of Memories would be a pretty awful stumble through the dark. While 358/2 Days is hardly necessary, it certainly answered a few minor questions about (SPOILER)Roxas and the Organization while building towards Birth By Sleep. Playing the Prologue of KH2 after completely Days certainly feels a lot more complete, and I'm one of those who already loved the Prologue.

I've done my best not to ruin Birth By Sleep for myself (and have so far done a fairly good job), but I understand that while it certainly brings up questions of its own, it is necessary for understanding how the events surrounding Sora were put into motion. I don't understand why it's a problem that the game might create as many if not more questions than it answers; it has been clear for quite a long time that the story isn't quite over, so why should all the questions be answered before it is? And even in the end, why should every question be answered?

Honestly, I'd still like to know what glaring holes there were in KH2. It doesn't wrap everything into a nice and tidy bow, certainly, but the plot is hardly Swiss cheese like people on this forum like to make it out to be.