Modern LEDs rule. I decided to use this colour combination, which is nicely visible even in bright daylight.
The red LED is cut down to about 65% of it's highest brightness, and the yellow LED is at 100%. This way, they both appear with about the same brightness. Different CF cards control the LEDs in a different fashion: Some pulse the LEDs shortly, so they appear more dim, and others keep it at full brightness until there's no more action for a certain period of time.
Hotplug works a lot better now. The CF standard gives CF card makers the freedom to switch to IDE mode if they detect a low-level on the mode pin for an extended peiod of time. A longer timeout has turned surprisingly many cards to hotplug-compatible!
There are drawbacks, though: Hotplug ONLY works in the left slot ("aux slot"), and it ONLY works with FAT-formatted cards. Since Amiga-formatted cards have an RDB and potentially more than one partition, it would make the mounter extremely complex. For data exchange with an Amiga, you might as well use a FAT-formatted card.
I've found one CF card that doesn't even support IDE mode. It's a "Hama"-branded 4G card (30MB/s speed rating) and the whole computer behaves funny if you insert it (no matter if hot-inserted or already in the slot when powered up). Seems to be shorting something - that's plain incompatible, and with the large number of low-cost cards that even work with hot-plug, I won't worry about this one.
All CF-cards that I have tried will be documented in the Wiki including a photo. I'm asking all testers to do the same: If you have a report about a card, please include a photo, so I can put that in the Wiki for others to make an easier buying decision.
In addition to that, all testers should have a nullmodem connection between the native A500-serial port and another machine. The current aux.scsi.device outputs debug messages on the serial port which will help us decide if a card is really incompatible, of if there's something we can do in software to make a certain card compatible. It's actually really interesting to watch the device driver negotiate with the card :-)