I've not heard of any reliability issues, just heat. However, in games temperatures are fine and that's what people bought it for after all (temperatures are going to be bad in Prime 95 and hot in Cinebench no matter the cooling, but that's not why you buy the processor).
I hope MSI releases a BIOS that allows a lower temperature limit to be set. Or AMD could clarify that 90C Is not the actual max safe temp. If I stress mine long enough it will register 90.xx degrees.
I set my 5950X to 87 degrees in BIOS and feel perfectly comfortable letting it render a video or something and walking away.
I would not sleep well if I let my 5800X3D run full load overnight.
AMD doesn't want these chips overclocked but I hope they give us the option to dial them back a bit in the BIOS.