Before I get started, I want to say that I'm not trying to tell people how to write their reviews, or saying that reviews that do these things are necessarily bad. These are merely things that bug me with reviews that I see constantly. Feel free to add your own, or tell me why I'm crazy for letting these bother me 
1. Writing a review as one paragraph
This is the biggest offender stylistically. Not even for reviews, but really any post on forums in general. This just makes everything really difficult to read, and gives the impression that there's no organization to a review, but simply random thoughts that came to the reviewer.
2. Writing a review by ONLY comparing the sound of the music to another band or album.
I think up to a point, comparisons to another band can be useful to the reader. For example, if the review says "If you like Popular Band X, then you should try this," then a pretty good amount of people who read the review will know if this music will or won't fit their tastes. But if the entirety of a review is comparisons to another band, it just seems lazy to not even attempt to describe the music for its own merit. Even if the comparisons are accurate, I think its useful to read what the music is like, rather than who it is like.
3. Breaking down every single song on an album
Whether this is the entire review, or just a portion, this one always baffles me. I really enjoy reading musical analysis, but when I read a review, the purpose is to find out if I will enjoy an album or not. While this could satisfy that purpose, it's a really roundabout way to do it, and isn't nearly as effective as describing the music in a general sense. Also, I think when reviews do this, it takes away the surprise from a first time listener (if they choose to read it). I don't think anyone would describe every chapter of a book in a review, so I don't understand why this gets done on this site so much. This also tends to make reviews extremely long.
Those are the big 3 that I notice a lot. I'll add more if I see them.