Nope, I haven't experienced this behavior so far.
Based on my experience, as long as ArcMap.exe is set as the external starting program in the project's debug settings page, when you build the solution, the add-in will be automatically put in the C:\Users\<user name>\Documents\ArcGIS\AddIns\Desktop10.0 folder. ArcMap can automatically discover add-ins from that folder and list them in the Add-In Manager, but you do still need to manually drag the add-in button/tool into the toolbar.