For SATA, they work great.What limitations do the SlimSAS ports have?
For PCIe/NVMe, their hotplug support is weird. They don't show up on the bus topology at all if you don't boot with something plugged in to the port, but you can do coordinated removal/insertion after that. But the fact that they don't show up means that it can cause everything else to get different bus numbers, so relying on bus numbers for naming interfaces and such can be problematic if you add or remove drives.