Cisco has recently released version 8.2(2)SR1 software for the 79x1 phones (not to be confused with the 79x0 phones!). This seems to fix many issues I was having with the phone randomly crashing, randomly unregistering lines and so on. I'd recommend this software load for EVERYONE running a 7941/61 phone. It is stable, and many issues have been fixed.
The Message Waiting Indicator (MWI) still has issues with a plain asterisk config. I have reported this bug to Cisco and I'm hoping they do actually fix it. In the meanwhile, the smart boys and girls in the Asterisk camp have added a "buggymwi=yes" option that you can add under your phone config in sip.conf to work around buggy Cisco phones. I'm not sure if this affects the 79x0 model phones.
I'm part way through putting Australian tones into the phone - but I'm having issues getting the dialtone to the correct Australian one. The File required is /Australia/g3-tones.xml in Cisco Call Manager - however it isn't publicly available on the Cisco web site. My current version (with the US dialtone still) is here.
Update 21/09/2007: Thanks to Tim who posted the correct Australian dial tones in the comments, this file is now correct for Australian locale. I have updated the file on the link above. Thanks Tim!