I enjoyed research hall until I wasted a decent chunk of time with the staircase. I'm not sure what happened but the first time I got to the switch on the very top, there was no prompt. So I was puzzled but moved on figuring I was mistaken. Either it was bugged or triggered by an event (which makes no sense). So that part was really annoying. I also felt that the rooms were repetitive. I get that it makes sense for the building but it wasn't up to par with the Lecture Building in vanilla. Fishing Hamlet was OK but felt like a less annoying smaller Forgotten Woods. Except for the short below ground segments, it was just scrappy houses. Valley of Defilement went off the crazy after you cleared the scrap wood, where Hamlet just led to Kos. Nightmare was sort of like vanilla Nightmare with enemies pulled from Cainhurst and Yharnam. It held most of the Yharnam look, which I'm glad was in the DLC in some regard but spiced it up a little. It failed to capture the freshness of Old Yharnam or Yahar'gul though.
So the DLC stages were C tier for BB. The bosses were basically the content that lasts. Ludwig was average for large scale, Laurence (FU Laurence) below average. Maria comes close to Gascoigne, Kos somewhere between Logarius & Gehrman, and the Failures were well, failures. If it wasn't for Maria and Kos, it would hard to the leave the DLC on a positive note, especially with the 2 boss scaling nightmares I endured.
I also experienced a sound bug on my last run to kill the 3rd appearance of Brador. When you go down below at the area with the bridges there are a ton of hounds. When a bunch were attacking me, the sound went crazy and then just shut off. I had a nice very quiet "You Died" to watch cause I dropped down haphazardly.