I once said, when this topic was discussed earlier, that it doesn't matter if there is one or two "can't download" -reviews among other reviews, but if your whole first review page looks like this:
1. ONE STAR: non si scarica (Italian and meaning "can't download")
2. ONE STAR: i can't download diz
3. ONE STAR: a me non mi si scarica !!!!! (again Italian and meaning "can't download")
4. TWO START: Error !? (I like this person, why 2 stars, nice pics?)
I can tell you that this really affects to the download rates.
The review should not be uset to tell people that you have messed up your phone so bad that you can't downlaod app's in to it. That is not reviewing!