Hi,
Your post is quite old, so I don't know whether my answer will be of any help to you now.
However, we use HA tags in our lab which are similar to His tags. We use the HA tag in conjunction with an anti-HA primary and fluorescent secondary antibodies all the time, with good results. You can basically expect the same sort of results you'd get with any other antibody to a cellular epitope.
Some tags are small enough that they can be replicated within your gene construct without any adverse effect on your gene/protein function. In our case, the HA tag is repeated seven times. The amplification of the recognition site for the HA primary antibody allows us to detect the protein with greater sensitivity than an epitope that is present only once in the protein.
Hope that makes sense