We've heard this from several people (hence this FAQ entry). To be quite honest, we don't really understand why.
We read online all the time about condensation inside the RV windows, and the responses are usually recommending dual pane windows. To be fair, we've never had single pane windows, so we have no point of comparison. However, we can say that we've camped in all kinds of climates all over the US and have never had any condensation.
So, yes… We still stand behind our decision to order our dual pane windows and will have them on any future RV also.