UberNZB indexes 132 groups and has free and open membership. The site started out in November of 2012. They got their own domain at the beginning of this year. They currently have a full year of backfill and a partial backfill spanning approximately 3 years, according to the site administrator.
Update: as of September 1,2014
Joining the Site
UberNZB is open and it doesn’t require an invitation to get a membership of the site. According to the administrators, the majority of the users on the site are free users at present. There is a VOP option, however. For $10AUD paid in Bitcoin or $12AUD in any other form, you can get an upgraded membership that includes a greater number of API calls and downloads each day.
All user info on the site is private and will stay that way, according to the administrators.
The goal of the site is to be a great indexer, according to the developers. They also want to remain free and open to new members. According to the developers, membership numbers are currently in the four figures range.
UberNZB uses nZEDb, which is an open source forked version of Newznab. The administrators do try to add to the project and to send those additions upstream in the development process. The servers the site uses are always changing, but they currently run Ubuntu server virtual machines on ESXi hosts. The backend of their indexing is independent of the website itself.
UberNZB Fully Supports RSS feeds.
UberNZB is run by IT professionals who all know one another. The indexes is constantly updated and the scripts that drive the updating process reset every hour. This helps to prevent any issues with lockups.
Free users to get access to the API, but paid users get more usage than free users. The site currently has approximately 2 million releases available, with approximately 2.7 million NZB files. If a listing is removed from the database for being spam, the files are kept available just in case.
UberNZB is currently hosted in Australia, but the administrators may change if it becomes necessary.
With free and open membership—and no invite required—this site is definitely one to check out. For a modest donation, if the site suits your needs, you can get access to the API more frequently than free accounts allow. UberNZB has enough backfill to make the site worth visiting and, with user information kept private, the site is certainly treating users right.