A quick AWS Powershell tools snippet post here. When you call Get-EC2Instance from the AWS Powershell tools it returns an instance object that has a Tags attribute, which is a Powershell list of EC2 Tag Objects.
I'm usually a fan of how the AWS Powershell Tools object models are setup, but this is one case where I feel there could be some improvement. Instead of using a list and forcing users to iterate the list to find the right tag, the EC2 objects "Tags" property should be a hashtable with the tag Key as the hash key so you can index directly to the object. But, this is was we have to work with for now.