1) When evaluating the options (mid 2007), Django and Ruby on Rails were the two projects with the most community momentum, and I personally put a lot of weight on that. I had used and was a fan of CakePHP, but the reality was that porting the mess that we had to either CakePHP or Symfony (the two we look most closely at) would have taken a significant amount of work. Since we knew that it wasn't possible to place development on hold, the main requirement was that whatever we did would need to live side by side with the existing code, and it was only a little bit more difficult to do that with another language and framework than another framework written in PHP.

I don't at all mean to say CakePHP or Sympfony would have been bad choices, but our technical team was such that switching languages wasn't a hurdle. I think the number of startups that have chosen Django or RoR as their platform of choice since mid 2007 in part validates our decision, but that doesn't mean other choices would have been bad.

2) It took 22 months to eliminate the last bit of PHP, but that was by no means the focus of development. During that time we made very large changes to the application based on things we learned from our customers. The reality is that no matter what technology we would have chosen, basically every single line of code would have been rewritten over the next two years. There was a little bit of us embracing technical debt in spreading the full port over 22 months: http://www.startuplessonslearned.com/2009/07/embrace-technic...

Thanks for the questions -wes