I thought about putting Win98SE on a small SSD for the heck of it, since it's not an OS that demands a lot of space and my new retro computing mobo of choice actually has a couple of SATA 1 ports on it.
Problem is, to get the most out of any SSD, you have to use AHCI, which 2000/XP onward wouldn't have a problem with, but I don't know if Win9x will even recognize the drives if not running under IDE emulation mode. Old OS, new hardware, after all. But for all I know, maybe those unofficial 98SE Service Packs patched in AHCI support...
EDIT: Well, turns out the motherboard I had in mind doesn't even support AHCI mode on its SATA ports for some reason, just IDE emulation and RAID. Maybe that wasn't added 'til SATA II.