Loss of cohesion but maintains puzzle quality.
The big key here is the game is all about puzzles, there are few books to read, very few characters to listen to, some unusual puzzle set-ups and very little computer/password interaction. But the fact remains that the puzzles are strong, they logically flow, and they mix trial and error with some demonstration. There are some puzzle standards throughout the levels, but there are some new tricks in store. Some puzzles may require a bit of back tracking, others will jump out at you very quickly. Although there are a few jumping puzzles- most are too easy to be even called puzzles. If you handled Black Plague's puzzles then requiem should be just fine.
However there are no monsters to fight against, or run away from. Only the odd visual/audio scare, there really aren't any abstract puzzles either. But there are still some very cleverly designed pieces. For example creating tracks of electronic boards to let power flow, using physics to place objects and block mechanisms, planting explosives to open shafts and a little bit of thinking outside the boxes. If you were a Penumbra fan because of the intricate involvement in a close knit world of monsters with puzzles and mind games, then requiem may not be for you. Requiem is all about the logical process in solving separate puzzle rooms, some very different from the previous. The core Penumbra elements survive, just not the full story driven cohesive package.