Specs:
Intel Core i3-3217U 1.8GHz
4GB DDR3, 500GB HDD
1366 x 768, Intel HD Graphics 4000
I ran it at that resolution, medium settings, no AA and it's alright. Turning off the bench, turning down the crowd, off the effects, etc. improves the framerate a bit more. In any case, it's certainly playable. Not perfectly smooth or anything, but what do you expect on an eleven and half inch (that's what she said) laptop? Turning players down to low does make it pretty smooth though.
So there is hope with a HD 4000! Obviously I would never recommend this (and certainly wouldn't recommend this laptop), especially in a laptop where you can't put in a good card, but it seems the power of the i3+ makes this a much more viable stopgap than Intel graphics did even just 18 months ago. I assume i7's and i5's improve the viability much more. And then there's Haswell.

TL;DR: If you have to get by with a HD 4000 it's not the end of the world. Not great or anything, but you can play the game fairly well on medium-low.
*Especially since it's....SINGLE CHANNEL RAM and you can't make it dual-channel.