Ok One last spoiler warning...seriously this WILL contain spoilers for the whole DLC, if you haven't played it, don't want to know whats in it or about the bosses, go ahead and turn your ass right around!
Ok completed the DLC today, done pretty much everything in it that I could find short of trying to farm for possible armour/weapon drops (I know I'm missing at least 1 weapon).
Difficulty rating: Bloody Tough.
Damn the DLC has some tough areas and enemies in it BUT once you figure out how they work and how to actually access the bonfires it does become a bit easier. The two non-optional boss fights are interesting and the final boss is a fight worthy of Kalameet, not amazingly hard but I would recommend bringing a friend for the first non-optional boss.
The optional boss however...bring friends, you WILL need them! If you go in solo you're essentially fighting a 3 man PvP gank squad with more health than regular players.
I was struggling with the enemies on New Game with a level 179 character at first due to probably a bit of overconfidence having through I had 'outlevelled' the DLC sufficiently to breeze through it. Yeah...don't be fooled, these guys WILL kick your ass if you're not careful about it.
Items: Fun and useful (most of them).
The weapons, oooh boy I've found a new love in the Puzzling Stone sword for PvP. Imagine if you will Ivy's weapon from Soul Calibur...yeah it's a Sword/Whip combo with an S rating in Dex. R1s are your standard shortsword attacks, R2s turn the sword into a whip, onehanded R2 is a standard whip attack followed by an extending poke attack, the twohanded R2 is a spinning attack which hits 360 around you and can be comboed into itself again fairly easily.
The Greathammer you can get...yeah don't bother, has horrible tracking and a kind of weird moveset and it poisons you, just use the Large or Greatclub...only thing it is useful for is being a bit closer to fully Cosplaying as the Turtle Knights.
The Drakeblood Greatsword is a Dex scaling Greatsword, nice to see that the prolifieration of weapons is now extending the other way (Str got a quite a few variations on normally dex focused weapons like the Red Rust Scimitar, Stone Twinblade etc.)
The Wrathful Axe (crafted from the first bosses soul at Ornifex) is basically a good scaling quality build halberd version of Sacred Chime hammer. The special attack (L2 triggers it) isn't that great but hey if you prefer the reach of a Halberd to the shortish range of the Chime Hammer, go for it.
The Spear crafted from Simh the Slumbering Dragon's soul at Ornifex is essentially a dex focused Lance instead of the strength focused Grand Lance, hits like a truck mind you.
I'm missing the Repeating crossbow that fires a Dark Bolt with the L2 but I have seen it in PvP.
Not really focused on Spells this playthrough but Second Chance makes a return from Demon's Souls as the Spell Denial only if only gives you like 10 hp so don't expect any OP'd things to go on with it. Tranquil Walk of Peace makes its return as well. Dark Greatsword spell is basically a Dark version of the Moonlight Greatsword projectile attack.
Overall opinion: THIS is what Dark Souls 2 should have been like IMO, the level is heavily interwoven, shortcuts in a manner similar to Oolicile township, fun puzzles, difficult yet fair enemies and bosses (except the optional boss, that can go fuck itself...ech...), interesting items.
You're looking at about 4-5 hours worth of playtime depending on how careful and how much you want to explore, for a full exploration I'd say add another hour and a bit onto that playtime.