I worked at Pivotal for 4 years. I think it had a great engineering culture, with a very principled approach to XP. This may not be for everyone of course. I learnt a lot there, it was a collection of people all wanting to become better, rather than simply delivering software.
After the VMWare acquisition, we'll have to wait and see how much of the culture remains.
As the NYC alumni "liaison" for the College of Computing at Georgia Tech, I've heard mixed reviews of Pivotal as a dev shop (not a flex; just trying to convey context).
Usually it's very great but in certain cases people feel like they spin their wheels on projects.
After the VMWare acquisition, we'll have to wait and see how much of the culture remains.