I played it through with the slayer during 2 free weekends on steam. Although it was funny at the beginning (the hit feedback was very good), it became much too repetitve very fast. More or less every level looked the same. Character customisation is also not really needed, I played though the campain with only using the first 2 skills you got as slayer. Itemisation is also meh, as you neither see any special properties on the items nor need to have a critical look at them. Just use the item that gives more damage and its good. The good thing is, I enjoyed the story. In short: highly repetitive, uninteresting skills and items but a more or less funny story. Don't buy! Especially not at full price. I think 10€ or $ would be ok for some people, but not for me.
Thew weakest part of the series, many bugs. On the other hand, greatest freedom. You can from the very beginning on travel virtually everywhere. If it were bugfree, 5 Stars. For me, I'd rather go with the third part.
