Through the years, my attitude toward reviews, both good and bad, has evolved. In the beginning, they were EVERYTHING. Make or break. But in recent times as my skin toughened, here are my thoughts:
I appreciate reviews, whether it's about my music, books, films, or any project I do. I appreciate both the good and bad, because in this industry you pretty much do have to take the good with the bad. When I review someone else's work, I try to do so in a way I would want my own work reviewed. If I enjoy it, I say WHY. If there were aspects of the story/album/film that didn't sit well with me, I say WHY. If I feel it was not categorized properly (and this can actually be more challenging than people think), I suggest another category it might be better for.
Any type of review can be helpful and even negative reviews - if explained well - can allow growth. But what is most important to remember is that a review is the opinion of one person and should never be viewed as a 'be all, end all.' Now, if there is a specific critique of your work that seems to come up frequently anytime someone gives a review, then perhaps this is something that should be considered.
Of course, not everyone is going to 'get' what you are trying to do, and as there are people out there who will find something they love about every piece of entertainment they consume, there are also those who absolutely refuse to enjoy anything they see/read/listen to. And sometimes, there isn't necessarily anything wrong with the work. Sometimes it may simply be a case of something like miscategorizing. Sometimes just changing the category listing can make a world of difference. While I don't dwell on reviews (nor do I recommend anyone doing so), they can be a good way of letting you know how your work is being received and if there is anything - whether it's the quality of the work or how it is being marketed - that might need a little tweaking. There are also times when fans will love one project but not be too crazy about the next.
The thing is, every great musician, writer, artist, filmmaker, etc has received both good and bad reviews. I actually do know many filmmakers, authors, and musicians who take that first bad review of their work as a badge of honor. To them, a small handful of bad reviews among several good ones basically says 'congratulations...you have now joined the ranks of every successful author/filmmaker/musician/artist who has ever lived.'
As for myself, I've never had a bad review affect my sales or downloads in an averse way, nor have I known anyone to whom that has happened. In fact, I have heard of some instances in which a bad review was actually the reason behind a sales spike/increase during a given week. Now, this isn't to say that you should half-ass your work. Always put your best forward. But also remember that if your work is being overall well-received, then a negative review here and there isn't going to affect it all that much. If it's the other way around though, then perhaps addressing possible issues with the work itself and/or marketing campaign should be considered.
Making and putting out your art is often a lot of trial and error. At times, it can be frustrating. I wish I could say there is a magical method, but there is not. Every musician, author, filmmaker, etc and his or her work is different, therefore requiring different methods of approaching the work in question. Even so-called marketing campaign experts don't always have it right. But the challenge can be a fun and invigorating one if the artist is up for it.
And in closing, feel free to review my work at sites like Smashwords, Goodreads, and CDBaby. :)