From our very first contact with Silvita we knew we were in good hands!  And our first impressions were correct.  While Silvita was not able to guide us personally (due to a family emergency which required her to be in Buenos Aires), she arranged for another professional guide to take over.  We were advised of this "glich" before we arrived in Ushuaia and had absolutely no problems with the idea.  Our substitute guide was marvellous.  She took us to the highlights of the National Park.  We had several interesting (not strenous) walks and learned so much about the history of the area,  the flora, fauna and of course the geography.  Both Silvita and our guide have lived in Ushuaia for many years and know the area well.    We were most impressed and,  based on our experience, would have no trouble recommending Tour HQ.