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No, the VPC itself isn't shared. Just the subnets within the VPC are shared. However, in most cases we use "shared VPC" instead of "shared subnets in the multi-tenant VPC" since the latter is cumbersome and most people immediately generally understand the idea.
How are the VPC subnets shared?
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From a management and financial standpoint, the resources you deploy to the Shared VPC reside in your AWS account. I.e., you have full access to manage the resources via the AWS console or APIs and you have full responsbility responsibility to pay for those resources via the standard Cornell AWS billing process.
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We are not aware of any AWS services that require VPCs and that won't work with the Shared VPC, as long as the service supports deployment to private subnets.
Can I use Elastic IPs in the Shared VPC?
There is nothing stopping you from assigning Elastic IPs to your resources in the Shared VPC. However, since the initial release of the Shared VPC offers only private subnets, assigning an EIP to a resource deployed to the Shared VPC still won't allow that resource to offer services to the public internet. I.e., there is no point to assign an EIP to resources in the Shared VPC.
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