In iTunes Connect you can supposedly view the customer reviews that users have left for your apps, it's under Manage Your Apps -> click on an app -> view details -> Customer Reviews. But in practice the Customer Reviews page is virtually useless.
Firstly, you have to select a country to view only the comments and rating from that country. Why is there no default option to view all countries at once? There is no way for me to check if there are any comments, other than individually clicking each of the 123(

!) countries.
Secondly, it's impossible to see customer reviews from older versions in iTunes Connect. So even if I individually check each country I still won't see everything. For example, I know that one of my apps has at least some comments from users from The Netherlands. But if I check that country I see nothing, because the app was recently updated. The older comments
are visible in the AppStore app, but when viewing the AppStore app I only see reviews from my "local" appstore, so won't see any review/ratings from for example Belgium or Germany etc.
I guess there are probably third party tools to do that. Forget "there's an app for that", Apple's new slogan for developers seems to be "there's a third party tool for that". But it seems to me that it would require minimum changes to just show a list of summaries and links per country ("USA 10 reviews 14 ratings, Canada 4 reviews 6 ratings" etc.) instead of a developer-unfriendly drop down list you have to individually click through.