The cache (up to 512k if you have the right chips) is said to work, but that is all. Under A/UX you got improved scsi with DMA plus cache.
It was designed with a view to improving performance of the AWS95 under heavy Appletalk server use, presumably involving the kind of small files mostly in use when the AWS95 was new and all the rage. There is a document somewhere showing remarkable increases in throughput with one of these installed.
Most mac OS will not boot with the card installed (I think 7.01 might), most units only have 256K cache as the other SIMM was optional.
It does speed up Appletalk (Appletalk pro 1.x came with the WGS95 install disks), probably 2x faster then a 950 without the card at all from what I remember.