Python vs. Go at Dropbox

Dropbox rewrote some infrastructure and produced 200KLOC of Go. They open sourced their common Go libraries. That's great. Some folks are saying this means they've abandoned Python. I don't read it that way. Dropbox needs to reduce costs and scale up if they want to have an IPO. Moving to Go seems like a natural choice for a company heavily invested in Python. Brad says Go gives you "90% of the ease of scripting languages with 90% of the performance of systems languages." That sounds right to me, but it makes the choice between Python and Go even more murky. I'm still searching for the dividing line.