Switching from SAS/SATA to NVMe for heavy traffic websites/web services?

Server storage technology is undergoing rapid evolution in the last years - platform vendors began to support directly attached NVMe SSD disks, which are theoretically many times faster than SAS/SATA disks, for similar price.

There are even some daring unorthodox voices that "hardware RAID is dead and a bad idea" in 2022. If not for SAS/SATA, then probably for NVMe drives, as they are so fast that they better be connected directly to a fast CPU or chipset.

One can find some reviews and comparisons of NVMe drives on technology websites, but many of the "performance disciplines" are often artificial, or of smaller relevance, and the relevant indicators, especially performance for many hundreds of independent processes doing random 4K reads/writes (heavy traffic webservers or databases) are poorly covered.

I'm looking for real-world stories with NVMe, whether they talk great success, disappointment or even disaster.