I went to Auschwitz and Majdanek on my own because I was in Warsaw.
I really can’t say I gained much from going. Between the ill-behaved locals and the just as ill-behaved student groups from EY (secular and national-religious) I thought I was at a theme park :(. Everything is just too refinished and too well-preserved for anyone to get a sense of the horrors of those places.
I was forced to take a trip for visa renewal purposes where I was living at the time and Poland was the best deal. Once I was there, I felt I had to go to the camps. I should have visited the ghetto and shul in Lublin on the way to Majdanek but I had no time.
I went to Auschwitz on a Sunday and had to use a very convoluted route (Poland is a Catholic country and Sunday is not a workday there). If you go from Warsaw to Auschwitz by train don’t go on a Sunday.