I run into a problem where my karma run hangs (see grunt watch hangs on karma:unit:run task). After digging into it I found out that it relates to problem #1 in post etc/hosts bug and dns resolution. Upgrading to 10.8 damaged etc/hosts. DNS resolution of localhost was extremely slow.
To fix this you could use 127.0.0.1 instead of localhost or split lines in
127.0.0.1 strug-imac.hypoport.local localhost
split them into single lines