Why don't see any reviews under reviews pivot in market place? At first I thought its because its pretty new market and there are none, but I can see them on web version of market place.
Do ensure that the marketplace on your phone and the web version belong to the same country. Your device's marketplace is determined by the first live account you use to sync with the phone.
Different country marketplaces will have different reviews by people belonging to that region. (In your case, the people to your region may not have reviewed the app yet)
For example, see the difference in reviews between
It can take a few hours for the reviews to be visible because of the results being cached. Also the reviews are grouped by region so it's a bit hard to see if there are any new reviews.
There are also external monitors that improve the way you can view your app stats like Distimo. in my opinion these sites are a lot better than the App hub.
There are also apps for Windows Phone to view your ratings. The one I use is AppTracker
The marketplace data is cached, and can take some time to show up. If you are seeing the reviews for your region on the web site then give it some time. It will be updated on the phone soon enough.
Since the AppTracker does not work enymore I found a working alternative: Review tracker app. Displays all reviews from all regions, also translates reviews from different languages to English.