Finally had some time to test
microdrives. I tested following microdrives with XTIDE Universal BIOS beta3:
Hitachi, 6 GB (model: HMS360606D5CF00)
Seagate ST1.2 Drive, 4 GB (model: ST64022CF)
Magicstor, 4 GB (model: GS10040A-11 47)
Hitachi and Seagate work fine, just like any CF card or hard disk.
Magicstor does not work properly for some reason. I can create partitions and format them. Formatting is a lot slower than with Hitachi or Seagate. Booting does not work with Magicstor. Boot sector is found but system freezes before any DOS strings. Same thing happens on a 486 with Award BIOS and large drive support. This means that there is something odd about Magicstor drive itself. It does work fine with a CF-to-USB adapter that i have.
Microdrives seem to be good drives as long as you avoid Macigstor drives. Microdrives are silent, have good transfer rates (they are faster than ISA can handle) and there is no write limit like on CF cards. CF cards have much better seek times since microdrives are real hard disks. Microdrives are a lot cheaper than CF cards with same capacity. There are lots of cheap microdrives on ebay: 2.5 to 6 GB models cost 8 to 13 USD with shipping.