[stevefink]

The showstopper for us when it came down to whether we will use VPC or not ended up being a no due to lack of support on elastic load balancing:

http://aws.amazon.com/vpc/faqs/#E13

I will certainly revisit this topic when ELB is inevitably available for VPC based customers.

[jvoorhis]

This can be worked around by adding a gateway.

Micro instances are also unsupported within a VPC, which is also a showstopper for some.