Samsung 980 SSD – A swift SSD without a DRAM cache?

Samsung is breaking new ground with the SSD 980 M.2 NVMe. This SSD does not have an EVO or PRO name to indicate that they are top models, nor a QVO name to indicate the budget segment. An interim solution, a middle class, and also one with clear strengths and weaknesses. When is the 980 a good buy, and when is it not?