They weren't so much behind twitter, as they were brought on partway through the game to help with some (I assume) scaling concerns.

(edit: I like pivotal, but keeping the quality on HN is essential to my being)

keywords: agile (whether you like buzzword or not)

It's more about changing the culture of Twitter engineering department.

Anyone know how much they actually cost though? Are their rates through the roof because people throw their VC money at them?

(from the article)

Sounds a bit hard to afford if you're not funded. I'd be curious to know what this includes too: how long, how many developers?

(Also from the article ;) )

Have any other open source efforts other than Diaspora come out from them? I don't understand how they let Diaspora do a big bang code release of such poor quality if they are the Rails experts they are reported to be.

Being co-located I would hope folks would have taken an interest and the Diaspora folks having enough maturity to ask for early feedback from the more experienced folks in the room from Pivotal or others.