Well, it's basically an extension of some of the old street circuits that used to hold events.
This video shows a short layout (about 1.2 miles) that is sort of the center section of the bigger F1 proposal (probably about 3.5 miles around). And while the F1 layout appears to be run clockwise, this iteration ran anticlockwise in this case.
http://www.youtube.com/watch?v=_lu_Q5afB5A
What I like about this one compared to Valencia are the elevation changes, the grassy areas, and the fact that there don't seem to be nearly as many of those extra little kinks and bends to mess things up in some critical areas. The braking zones look more straightforward, with with better opportunities to get alongside someone before the major braking zones. Also, Mar del Plata has five good "straights", which are pretty straight for the most part, whereas Valencia really just has two, with the other three flat-out stretches having more significant corners in the middle of them.
Even with Tilke "designing" this, the existing roads, buildings, etc limit what he can mess with.