Did you seriously consider a traditional colo or other vendors like SoftLayer (e.g., Rackspace)? It seems like at some point your reasoning here will apply to a colo if you grow bigger.
Re: Rackspace and other providers – based on my real-life practical experience with a few of the largest providers in the States, SL quality of services and their provisioning speed are miles away from competitors could offer. So it was a no-brainer to go with SL and I'm happy we did.