Re: Tried Amazon custom metrics? Compuware? Cedexis?
Your questions highlight the differences between monitoring of apps you host on IaaS (e.g. Amazon Web Service, Azure, etc.) v. monitoring of 3rd party SaaS apps like Salesforce.com, Dropbox, or Office 365 (full disclosure up front - my company is working to address these cloud visibility gaps).
If an app I manage is on AWS, their data feeds will give me some useful data, at least on the health of the VM's and their infrastructure. If it's a custom app, I may want to also use something like New Relic and/or some external synthetic solution like Compuware to give me more insight into my app's performance and user experience.
The challenge for IT teams consuming 3rd party cloud applications, like Salesforce, is that the service level they receive depends on the health of all the infrastructure between the users and the service providers. Just getting a feed from the application service provider isn't enough. IT needs to be able to test and monitor the end-to-end service delivery chain.