Okay, this is interesting.
I have the above tablet, which has drivers for both xorg, and the kernel.

I've been reading on using the hal FDI files, and I have such an FDI file, which detects the tablet correctly. Hal-devices report below.

The problem is no pressure sensitivity/configuration (the device moves the cursor, and I can click, but that's it). xinput does NOT list the tablet as a device, so I can't configure it as extended input devices in GIMP etc. I know it is supported, because I've had pressure working before.

The interesting thing is that if I do the old way of configuring (with xorg.conf) it WILL be listed in 'xinput list', but any attempt to move the stylus will crash X. (which is why the new FDI interface must be used.)

Does anyone have ANY thoughts as to what I can to to get the device to appear? My fdi file is below.
Also, xorg.0.log offers no indication that the 'aiptek' driver is being loaded... (whereas if I alter the xorg.conf it does get loaded). Can I just add an InputDevice section containing only a "driver" line to get xorg to force-load the driver?

hal-devices output:

1: udi = '/org/freedesktop/Hal/devices/usb_device_8ca_20_noserial_if0'
  usb.linux.sysfs_path = '/sys/devices/pci0000:00/0000:00:1d.0/usb5/5-1/5-1:1.0'  (string)
  usb.device_revision_bcd = 256  (0x100)  (int)
  usb.max_power = 50  (0x32)  (int)
  usb.num_configurations = 1  (0x1)  (int)
  info.subsystem = 'usb'  (string)
  usb.num_ports = 0  (0x0)  (int)
  info.product = 'stylus'  (string)
  info.udi = '/org/freedesktop/Hal/devices/usb_device_8ca_20_noserial_if0'  (string)
  usb.linux.device_number = 6  (0x6)  (int)
  input.x11_driver = 'aiptek'  (string)
  usb.device_class = 0  (0x0)  (int)
  linux.hotplug_type = 2  (0x2)  (int)
  usb.device_subclass = 0  (0x0)  (int)
  input.x11_options.Type = 'stylus'  (string)
  linux.subsystem = 'usb'  (string)
  usb.speed = 1.5  (double)
  info.linux.driver = 'aiptek'  (string)
  input.x11_options.USB = 'on'  (string)
  usb.device_protocol = 0  (0x0)  (int)
  input.x11_options.Mode = 'absolute'  (string)
  usb.version = 1  (double)
  input.x11_options.SendCoreEvents = 'true '  (string)
  usb.vendor_id = 2250  (0x8ca)  (int)
  input.x11_options.zMin = '0'  (string)
  usb.is_self_powered = false  (bool)
  input.x11_options.zMax = '511'  (string)
  usb.product_id = 32  (0x20)  (int)
  input.x11_options.ZThreshold = '0'  (string)
  usb.can_wake_up = true  (bool)
  input.x11_options.Pressure = 'linear'  (string)
  usb.interface.number = 0  (0x0)  (int)
  input.x11_options.KeepShape = 'On'  (string)
  usb.interface.class = 3  (0x3)  (int)
  input.x11.identifier = 'pen'  (string)
  usb.interface.subclass = 1  (0x1)  (int)
  usb.interface.protocol = 2  (0x2)  (int)
  linux.sysfs_path = '/sys/devices/pci0000:00/0000:00:1d.0/usb5/5-1/5-1:1.0'  (string)
  info.parent = '/org/freedesktop/Hal/devices/usb_device_8ca_20_noserial'  (string)
  usb.vendor = 'Aiptek International, Inc.'  (string)
  usb.bus_number = 5  (0x5)  (int)
  usb.product = 'USB HID Interface'  (string)

FDI file:

<?xml version="1.0" encoding="UTF-8"?> <!-- -*- SGML -*- -->
<!-- Aiptek:  Medion Md9570; Trust Wireless Tablet TB-3100 -->
<deviceinfo version="0.2">
    <match key="info.linux.driver" contains="aiptek">
      <merge key="input.x11_driver" type="string">aiptek</merge>
      <merge key="input.x11.identifier" type="string">pen</merge>
      <merge key="input.x11_options.Type" type="string">stylus</merge>
      <merge key="info.product" type="string">stylus</merge>
      <merge key="input.x11_options.USB" type="string">on</merge>
      <merge key="input.x11_options.Mode" type="string">absolute</merge>
      <merge key="input.x11_options.SendCoreEvents" type="string">true </merge>
        <merge key="input.x11_options.zMin" type="string">0</merge>
        <merge key="input.x11_options.zMax" type="string">511</merge>
        <merge key="input.x11_options.ZThreshold" type="string">0</merge>
        <merge key="input.x11_options.Pressure" type="string">linear</merge>
        <merge key="input.x11_options.KeepShape" type="string">On</merge>