Didn't check with synaptics but apt does the job, just got todays build 14184:
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
xbmc xbmc-common xbmc-skin-default
3 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 44.5MB of archives.
After this operation, 16.4kB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
xbmc xbmc-skin-default xbmc-common
Install these packages without verification [y/N]? y
Get:1
http://ppa.launchpad.net hardy/main xbmc 2.1a2svn14184-hardy1 [490kB]
Get:2
http://ppa.launchpad.net hardy/main xbmc-skin-default 2.1a2svn14184-hardy1 [13.9MB]
Get:3
http://ppa.launchpad.net hardy/main xbmc-common 2.1a2svn14184-hardy1 [30.1MB]