EDIT: Also, Apple doesn't display ratings like Google does, so there is clearly no reason for them to leave reviews like that.
A 3/5 isn't a good rating in any country I've lived. A 5 is good. There isn't really a rating for "exceptionally amazing". But I'm sure somewhere, a 3/5 means "pretty good" and 5/5 is reserved for exceptionally positive reviews.
So the problem with world wide rating is that are so different depending on your location and culture (and age).
Although I only install apps that have 4.5 star rating so I am being hypocritical...
A long time ago when I was in school in Norway, grades was marked on sort of 1-5 rating. (LG=Not very Good, NG=Quite Good, G=Good, MG=Very Good, S=Exceptionally Good. http://no.wikipedia.org/wiki/Karaktersystemer_i_Norge#Grunns...) As I was usually among the best I mostly got a grade in the range of MG ie a 4. The top rating was practically impossible and I only got that on a few occasional tests but never on a full year's grade. MG+ was the more likely top grade to aim for. (They have since changed and expanded the grade system)
When I then moved to the UK in my last years of schooling, grade A seemed to be handy out all over the place. I do remember having to have meetings with the head of the year to be put into the best Maths set even if my average from Norway was not of the top grade and trying to explain that top grade in the two countries was not equivalent.
If I think the app is good, and other people should download it, my rating makes the most difference if I award a score of 5.
If I think the app is OK but not worth downloading, I can most effectively indicate that by scoring it a 1.
If I want people to read my review (as Turkish reviewers have observed), I should perhaps rate it a 1 as well.
So, if I want my reviews to have an observable effect, I should (perhaps) rate everything 1 or 5.
(Or, I could decide what rating I want the app to have, then rate it a 1 or 5 depending on which direction I need to move it)
The motivation initiated by Apple here is bad - by simplifying everything to a single figure average, we lose all the nuance that you are trying to give with your Norwegian-style ratings.
You just re-discovered strategic voting. And that's why the rating system should display the median and not the mean. For the median, you can skip step two: just vote what you want.
In my case,
5 stars = Does exactly what I want;
4 stars = Does most of the things I want, minor features missing;
3 stars = Has a few useful features, the rest are irrelevant;
2 stars = Frequent crashes and major bugs;
1 star = Does not install or start at all no matter what I try (very rare).
I mostly give 4 stars, but there are a lot of 5 star worthy apps, as well (Pocket Informant and ES Explorer, for example).
Bimodal rating distributions everywhere. Help!
I've always hated Yelp and found it useless until I went on holiday to US. In Australia, there's just so few places on it its kinda boring.
There are also people on ebay  offering five star reviews for around $15.
A 1/5 would be the highest score, and 5/5 would be the worse score.
4* ok but has some issues
2 and 3: irrelevant