In the very rough example which I posted, those are all tags that you see, including those with flowrates, pipe size, system reference etc.
I'm sure you already know, but for the benefit of others, before you annotate a 3D view its orientation must be locked.
You can customise tags to your particular purpose, for example if you want every valve to have a unique reference then the tag would read the "mark" value perhaps. Or use keynotes etc.
You can quickly tag all items or groups of items using the "tag all" option on the annotation ribbon
Text can be added as you wish. You can rotate the text to align with the isometric axes but I don't think you can slant text at +30 and -30 degrees as you would probably normally do in Autocad (maybe someone could clarify this but I can't see an "oblique" option). Unfortunately you don't seem to be able to rotate tags to isometric angles, only horizontal or vertical.
As I said, dimensions are a bit of a problem. You can dimension between items or from end-to-end of pipe sections etc but Revit appears to want to place dimensions on the bottom extent of the view so instead of appearing along the pipe they appear below it as if on the floor.
Hope this is of some assistance.