OTA Update Center is now offers OTA updates to ROM developers for free. OTA Update Center has not brought a unique OTA service as the same services have already been provided by ROM Manager and Goo.im Manager. To work with OTA Update Center you have to install an app on your device which interconnects with the servers to pass out OTA updates to anyone using the ROM.
But Developers are no longer uses OTA services to make its ROMs simple with less codes, so if you’re a user, then you will have to see either ROM developers use OTA Update Center or not.
Source: OTA Update Center