Lets you upgrade your Pricing Tier even though your P.A.Y.G Subscription is out of CPU cores
It let me migrate my SQL Server VM to a higher Pricing Tier without first checking if I had enough CPU cores left in my Pay As You Go subscription. I didn't even know I had a limit till now that I had to check.
It merrily upgraded my Pricing Tier, however the VM would not start. Would give me an error that wasn't very specific until I looked at the error details.
You should check the available cores first BEFORE allowing the user to migrate.