Except for one of the largest Microsoft network features, Active Directory, isn't supported on the Surface.
Also, with the iPad you actually do have native, ARM compiled applications running. In Windows RT, you are only able to run HTML/JS apps. JS is fast, but it still pales in comparison to the speed of native code.
It's Microsoft's fault that people expect the RT tablets to be something that they're not. They propositioned it as a laptop with their cases, and then proceeded to leave in the Desktop UI. It's not a hard leap to assume that it should function as a desktop Windows machine.
Microsoft needed to either ditch classic UI entirely on RT, and actually buck up and make true Metro Office; or they needed to embrace the classic UI as a first class citizen and allow apps to be compiled and targeted towards it (and published on the marketplace).
Instead, in typical Microsoft fashion, they managed to do the wrong things for both. Leave in Desktop UI, Make Office the only non-OS application that can run there, and overall make the experience confusing and deceiving.