I read them but would never base my choice on one person's opinion. It also helps if you can read several reviews by the same person to see if nothing would ever make this person happy or if they had (in their opinion) a legitimate complaint.
Having been cruising since 1964 I have really only written 1 bad review. Someone reading it might think I am one of those who could never be pleased but if they read my other reviews they might realize I may have had a legitimate complaint.
Cruising isn't perfect- nothing is - but going in with a great attitude and addressing any problems you might have with the proper people calmly and quietly can usually take care of anything that has occurred and doesn't warrant you writing a scathing review when you return.