Drupal as a solution for start up companies

I'd love to hear the opinion of the Drupal community on this subject. Is Drupal a good platform for Internet start ups looking to ultimately expand on a global scale. We've gotten a lot of negative feedback when trying to market some start ups under the Drupal platform. Mostly it comes from having to recently defend Drupal to potential investors of Internet start up companies. For the most part when we're meeting with these people as soon as the word Drupal comes from our team's mouth they frown at us.

Their largest concern is that there is a large misconception that Drupal is slow. Personally I feel like slow Drupal sites are mis-configured Drupal sites. But it goes on past that. The number of bugs filed against the core. They are quick to suggest that we use [insert buzz word of the week here], because it's a much better solution. “You need to be using Ruby on Rails, Twitter was built on Ruby on Rails, so obviously that's what you should be using.” (I'm not saying there is anything wrong with Rails at all. It's a powerful language. I'm just tired of hearing that RoR is faster than Drupal just because it is. I've yet to come across any finite numbers, or actual evidence to support that either is faster than the other.)

An interesting counter point is that the core isn't truly OOP. Which in my opinion still follows some core concepts of OOD. I feel that OOP is a very powerful tool, not the ultimate answer for everything. So again this to me comes off as not using a very popular buzz word. Although there can be interesting arguments made for both sides in Drupal's case. I'm interested to see if the core shifts to more traditional OOP for the release of 8 as PHP continues to mature as a true OOP language.

My opinion is that Drupal is an extremely powerful and versatile tool, not an ultimate answer. That being said, I feel as it's a perfect fit for start ups. It removes the need to reinvent the wheel on so many things during development. I mean can we really improve that much on a user login system? More importantly, it adds an excellent and proven security layer. The top reason that I choose Drupal for our start up platform is that Drupal extends and integrates so well with other applications. For me this is the most powerful aspect of Drupal.

What I'd really love to know is what the Drupal community's opinion is on the subject of using Drupal as a platform for startups. Does anyone know of any highly successful start ups that have used Drupal? More than just using Drupal as a solution for our startups I'd love to bust some of these stereotypes in the minds of those outside the Drupal community.

Drupal is just like Word Press or Joomla.
Drupal is to big and as such to slow.
Drupal has to much overhead because it does so much.
Drupal isn't python, or RoR therefore it can not succeed as they have in the past.