I can confirm that XDMCP is working on debian squeeze.
Stranger than that is a box I have running Lucid, which does work with XDMCP although this is declared broken for Lucid.
On another box that I upgraded from Lucid to Maverick, XDMCP was working before and stopped after the upgrade.
This reminds me of the pulseaudio saga, in case you still remember.
I can confirm that XDMCP is working on debian squeeze.
Stranger than that is a box I have running Lucid, which does work with XDMCP although this is declared broken for Lucid.
On another box that I upgraded from Lucid to Maverick, XDMCP was working before and stopped after the upgrade.
This reminds me of the pulseaudio saga, in case you still remember.