In Python 2: always inherit from object explicitly. Get the perks.
In Python 3: inherit from object if you are writing code that tries to be Python agnostic, that is, it needs to work both in Python 2 and in Python 3. Otherwise don't, it really makes no difference.
The following snippet fails due to email package's LazyImport mechanism, only in Python2, no LazyImport in Python3 in email package:
>>> import email
>>> import sys
>>> for name, module in sys.modules.iteritems():
... try:
... print name, module.__file__
...