SSDs have wear which will lead them to eventual failure. Wear land nearly as bad as a few years back, but you can still only write to a cell for only a limited amount of times. If you're constantly writing data to your disks, you may need something that doesn't die.

I would personally go with a "normal" RAM disk in this case, but CPUs only have a limited amount of RAM and memory channels available. Complex operations on RAM disks may also increase the load on the CPU which can be a performance downside if you're doing things like compiling large code bases. Coupled with a battery backup, this looks like a pretty neat solution to SSDs for write-heavy operations, assuming you persist the important data periodically on something else (such as a hard drive).

I'd be wary of bit flips running this card, though. Without ECC, bitflips in RAM are just something you should be expecting. Normal RAM doesn't operate with the same data for an entire year, but this semi-permanent setup may be more vulnerable to bitflips.

I know RAID cards will often contain a battery backed RAM cache for file operations in case the power goes out, perhaps this card can be useful for that as well? With ZFS you can set up all kinds of fancy buffering/cacheing and I imagine an SSD write cache would show wear and tear much faster than one of these cards, and you can't exactly hot swap M.2 cards. A couple of cheap gigabytes of persistent write cache may just be the solution some people have been looking for.