I generally enjoyed C:OoE. I had very few problems getting through to the end, despite a few tough bosses and the occasional glyph hunt. In fact, I found it no more difficult than any other games in the 'metroidvania' series. The glyph system is fantastic and provides a much more strategic approach to defeating tough enemies and bosses.
Unfortunately, my premature usage of a food item called 'tasty meat' prevented me from fulfilling the villagers' quests at 100%. Apparently 'tasty meat' shows up in a few choice areas and then never again, (believe me, I've wasted a few hours re-searching for the item, hoping for it's appearance in a green chest) so if you snag the item in the few places where it can be found and use it (which I did early on, unfortunately), then you're screwed. I didn't realize it would turn out to be such a pivotal item. Jeers to a design mechanic preventing full completion of the game based on a rare usable health item.
I agree with bluesyncopate, that despite my continued appreciation of the tried and true metroidvania style, I'd like to see an attempt at a more straightforward 2D approach to the series again, perhaps via Wiiware.. The first, third and fourth stateside entries remain my favorite. Maybe 'level packs' that chronicle the journeys of different characters from the Castlevania universe in different time periods, but again, played out like old school Castlevania. This could culminate in a final level pack tying together their stories (but no worries, it wouldn't be a fighting game).