Not sure if PS3 is supported yet. I am running the release candidate at the moment.
I've installed Posh-Hg into my profile. When I open up PS I get the following message:
Id #5 | Release:
| Updated: Jun 21, 2012 at 6:34 AM by mwrock | Created: Jun 21, 2012 at 3:05 AM by jkells
End qouting a commit message results in an interactive shell'ish mode.
ctrl-c breaks it.
C:>hg ci -m"this is mig terminated commitmessage"
Id #3 | Release:
| Updated: Feb 9, 2012 at 10:35 PM by NikolajW | Created: Feb 7, 2012 at 2:07 PM by dalager