Mercurial 3.5 has progress enabled by default.
Earlier versions can use the standard progress extension shipped since version 1.5. Simply enable the extension by adding this to your hgrc file:
[extensions]
progress =
You will then see progress bars on clone, push, pull, and other operations. The progress bars are only shown after an initial delay of 3 seconds by default. You can easily change this by adding:
[progress]
delay = 1.5
to your hgrc file. See hg help progress after enabling the extension.