Add press release commentary

text/0001-cdk-update.md

@@ -53,10 +53,6 @@ const myDevelopmentStack = new ApplicationStack(app, "StackNameForDev", {
 The `interactiveUpdate` property is optional, and when present and `true` the
 `cdk update` functionality will be executed on the stack.
 
-> **note:** I chose in-stack markup instead of a `cdk.json` flag so that if
-> there is an L3 construct for a personal development stack (or a library that
-> creates them) then the attribute can be set there instead.
-
 #### Running Update
 
 To run a one-shot update, you can invoke the `cdk update` command on some or all
@@ -158,7 +154,16 @@ without a full CDK deployment. When the `update` command can identify that all
 changes in the stack have shortcut support, it will directly publish the assets
 to AWS and then modify the underlying CDK resources directly.
 
-> the rest of the PR goes here. Eugh, PRs...
+> Using cdk update dramatically improves our development iteration speed for
+> Lambda functions. It cuts down the change-deploy-test cycle to seconds, where
+> it was minutes before with a full cdk deploy each time. Unlike some other
+> solutions, it actually updates our function running on AWS, which means there
+> are no problems with the Lambda behaving differently during testing, and then
+> in production - Adam Ruka, developer
+
+Any CDK users who are deploying code to Lambda functions or containers on ECS or
+Fargate can take advantage of this tool today, by configuring their stacks for
+interactive update, and then using `cdk update` instead of `cdk deploy`.
 
 ## FAQ
 
@@ -205,7 +210,9 @@ This solution has a risk of introducing a deployment tool that users might use
 to shortcircuit the safe CloudFormation deployment process. If a user runs CDK
 update on their production stack, it can perform updates without adequate stack
 update safety checks. Releasing a public tool with instant update capability
-into the CDK may not be the right way to make this functionality public.
+into the CDK may not be the right way to make this functionality public. To
+mitigate this, `update` only runs on stacks that have explicitly opted in to the
+capability.
 
 ### What changes are required to enable this change?
 
@@ -215,7 +222,13 @@ This RFC requires three changes:
    examine the Application stacks for updates that can be applied and apply
    them.
 2. Adding the `interactiveUpdate` flag to the `StackProps` object, allowing a
-   stack to be configured for interactive update.
+   stack to be configured for interactive update. This property will default to
+   `false`
+
+   **note:** I chose in-stack markup instead of a `cdk.json` flag so that if
+   there is an L3 construct for a personal development stack (or a library that
+   creates them) then the attribute can be set there instead.
+
 3. An expansion of the CDK asset model to include optional construction process
    metadata and construction input metadata. This is required to allow CDK to
    identify input changes to the asset, reconstruct it from the defined