I think you need a Windows Azure account, not a windows box -- I've seen someone using VS Online on Macbook Pro/Chrome, IIRC. (Can't remember where, though.)
Scott Hanselman used an Azure VM to run VS2013 and tools, and remoted into it from a coffee shop using a Surface 2 (the 'RT' flavor, not a full desktop). It's a nice way to work from lower power machines. To do this, of course, does require an Azure account, and after your 'intro' phase would be paid.
The support services provide things like source control, work item tracking, and similar 'in the cloud' but they work with your VS2013 install, wether on a desktop or on a VM on Azure.
What you have probably seen is something like this: http://www.hanselman.com/blog/UsingASurface2RTARMToGetActual...
Scott Hanselman used an Azure VM to run VS2013 and tools, and remoted into it from a coffee shop using a Surface 2 (the 'RT' flavor, not a full desktop). It's a nice way to work from lower power machines. To do this, of course, does require an Azure account, and after your 'intro' phase would be paid.
The support services provide things like source control, work item tracking, and similar 'in the cloud' but they work with your VS2013 install, wether on a desktop or on a VM on Azure.
Hope that clears things up!