Here is how I got some acceptable results:
Logged as Admin, create a reports' Folder.
Move the reports you want to get from API to that folder.
In the reports' list, look for your folder and click over the dropdown arrow that appears next to it; A set of options will be shown, then, select the Share option and share it to users, roles, or groups you want to give access to the reports via API.
In your app (I have a .net project for that) query all reports with a something like this:
HttpGet(token.instance_url + @"/services/data/v29.0/query/?q=SELECT+Name,Description,DeveloperName,Format,IsDeleted,LastReferencedDate,LastRunDate,LastViewedDate,NamespacePrefix,OwnerId+FROM+Report+ORDER+BY+Name+ASC", "");
This in my case, returns metadata information of reports within the created Folder.
This metadata information contains report identifiers. Eg. 00Oi0000005iqNhFEI, but does not contains the real report information (the records, the tables and sales information)
5 . To get real data of a specific report, it is needed to perform another query using the identifier of the report you want to retrieve. You can do it with something like:
HttpGet(token.instance_url + @"/services/data/v29.0/analytics/reports/00Oi0000005iqNhFEI?includeDetails=true", "");
Note that I'm using the report's identifier and also the "analytics" path
and well, this query is the one that will give you the real report data.
Hopely this will help somebody.
I'm pretty sure this is not the best technical explanation but really, that is the way I got it working.
Any comments, critics, tips, anything are always welcome.
Thank you to Peter Knolle and Mohith Kumar for the help