Just a waste of time.
Killing things to get better items to kill bigger things is at the core of KUFCOD, just as it is at the core of every other game of this type. KUFCOD does not fail for being unoriginal, it fails because the core game play is simply not interesting. Weapon combat is limited to jamming on the X button and watching the same animations over and over, and as simple as this sounds, it doesn't work. With a few of the six character the last two attacks of the string cannot be stopped once started, sending the character flying off in one direction while the enemy has sidestepped and is wondering where the hero is going in such a hurry. This is not to say that the monsters are smart, they arrive in mobs, surrounding but rarely attacking, leaving that to the annoying archer bastards who can somehow shoot around corners and over hills.
Repetitive combat can be forgiven if weapons and the monsters being killed change often enough, which is something else KUFCOD fails to do. In each of the stages there are only 4 or 5 different enemy types, but even between the stages many of the monsters are just pallet swaps of each other, leading to a dreadful familiarity in every encounter. When killed they drop weapons and armor, but most of it looks the same when equipped and animates the same when attacking. There is an item creation system, but it is poorly explained and creates nothing beyond the same weapon plus 1. It is also a necessary evil: special attacks do very little to help or change the broken hacking and slashing.
As a character levels new abilities are not automatically gained. They are instead 'learned' by choosing a new ability and killing the requisite number of monsters. This would work well if the requirements followed what was actually in the levels, driving the player forward into new territory. Instead many of them require backtracking, most are spread across multiple levels and there is no way to know this ahead of time. Only two abilities can be in the learning queue, and if one is removed to make space for another before it is finished then the killing count is reset, forcing more backtracking. There is even a skill I found that required a hidden boss to be killed who wasn't available for the character I was playing; truly a waste of time.
Quests fair no better: all of the missions are fetch quests. There nothing inherently wrong with a fetch quest as long as it is accomplished while moving forward or while on the way to do something else. Fetch quests in KUFCOD are ambiguous, full of backtracking and needlessly repetitive. One quest required that I play through an entire level five times to get everything I needed. After two times, I gave up, surrendered, shut it off and played something else. It was Wednesday, and there were new Rock Band tracks that required my attention.
I put up with Kingdom Under Fire: Circle of Doom for around 14 hours before throwing in the towel. That was 14 hours of X button abuse and carpal tunnel damage, and I haven't even gotten to the poor level design, below average graphics, terrible voice acting, laughable story, and multiplayer that does nothing more then spread the misery around, but there is no need. The only people who should play KUFCOD are developers of new hack and slash games, and then only so they know exactly what not to do. No one else should bother. If you really, really need to kill things for phat loot pick up Arkadian Warriors on Xbox Live Arcade: its $10 and better in every way.