I've enjoyed playing Resident Evil from the beginning. Resident Evil 4 was a big departure from what people had become used to losing the rich pre-rendered backgrounds in favour of 3D environments. The problem with this game is it deviates a long way from what made the original so great. Not just in terms of the story but also the game mechanics.
The inclusion of a partner is not a good one, often you will be cursing how the computer controlled AI manages to get itself killed and while playing with a mate online is satisfying this is no longer Survival Horror as the tension of feeling alone is gone and you will only feel despair from running out of ammo when your partner carelessly wastes it.
The only real remaining mechanism is that of how your character has to stand still while firing a weapon, this leads to repeative shoot run shoot moments and does not feel as free flowing as games such as Dead Space for example.
Overall this game will either be loved or hated, those who feel it has deviated too far will find reason to hate it while others who enjoyed the fourth game will find plenty here to keep them occupied.