@effy:
IDE to SCSI adapters are perfect for Amigas. The speed is not lost as usually your controller can push anywhere from 7 to 10MB per second, so it's an ideal solution for not paying lots and lots of $$$ for authentic SCSI gear, as you will never push a CDRW or a hard drive to its potential limit.
In the PC world, it's still better to get genuine SCSI, as speeds that these converters offer are often not as fast as real SCSI would offer, so while they are a nice alternative, the real thing is still superior as far as the up-to-date standards and speed requirements are concerned. :-)