Very hard, but rewarding when you get used to it
Your character doesn't level up, instead you get better at playing. If you don't study the boss's moves and attacks you WILL crash and burn sometimes literally or freeze and become a snowman.
The camera control will get some time getting used to, and the game doesn't have an auto-aim function, which will be a bit troublesome when fighting agile monsters like the raptor type monsters. Once you found your own strategy to a single monster type, you have to find another strategy to another different type and another strategy still for a boss while in rage mode
e.g. you can hit, run and still not get hit while fighting a congalala while its raging but you will mostly be hiding from a tigrex with its double charging speed
There are also many types of weapons and some are more effective to the different parts of a monster e.g. slicing weapons can cut off the tail of some monsters and blunts can break the protective shells of other monsters
When you have learned the ways, strategies etc. then it gets rewarding like your first tigrex kill or killing the gigantic lao-shan
all in all great game for those who likes a challenge