These PU's gave my cheapish Epi Les Paul a new level of versatility an d allowed for brighter tones that were not accessible before. The P90s are very good. The single coils are a bit thin in my opinion and I have not managed to get "quacky" Strat-like tones from my Les Paul with these PUs. In my opinion, the parallel humbucker setup sounds very clear, while the serial humbucker setup is fatter and perhaps slightly muddier.
Overall I am very happy with my purchase.