I also pay attention to rewies and possible scam accusations. Unfortunately, there are also some exchanges that are made to scam people so I'm always careful.
I couldn't agree more with the factors listed as important to you. However, in addition to these factors there are others which helps us distinguish good exchange platforms from the bad ones, and some of these includes, of course, the list of currencies it supports, exchange fees, user-friendly interface etc.
In any case, these are the some of the factors I consider when deciding which exchange platform to use.