groupadd test
useradd test1
mkdir /tmp/test
chgrp test /tmp/test
chmod g+wrxs /tmp/test
echo 'umask 007' >> /etc/bashrc
su - test1
touch /tmp/test/d
ls -laF /tmp/test
drwxrwsr-x  N root test 4096 <DATE> ./
-rw-rw----  N test1 test 0 <DATE> d

Now if you create an empty file in /tmp/test with nautilus, it will look like:
-rw-------  N test1 test1 0 <DATE> bug

Instead of what /tmp/test/d which was properly created.
Since umask is defined, I would hazzard nautilus is improperly setting
permissions instead of leaving it to the underlying system...

This poses a small usability problem more likely to hit in corporate
environments: now users have to make an extra step they don't need... to
actively set permissions on some files in certain directories they shouldn't
have to have to bother doing it.