I am nearing the fourth boss and having an absolutely blast with this. There's an artificial difficulty increase at the second boss that basically tells you "you're not supposed to be here yet". After a handful of defeats I decided to spend (more) time at the Shops and levelled up Shards, bought new items, purchased a well nice vertical slicing great sword, explored the levels and all that. All is well now and am a fantastic time with this.
Weapon of choice: great sword. Slow but hits enemies both above and below.