Mine is originally using Baconreader while in the dorm community bathroom doing a deuce and seeing a mention of Sync. Installed and instantly became a user. Later on I had a problem with the app because I was running beta Android. Reached out to the dev and after a few fix attempts an update was posted that fixed the issue. To get that kind of support is rare and is why I have continued to stand by Sync all these years.
I used to use AlienBlue on my iPod touch way back in the day haha. Eventually got an Android phone and tried out a couple of apps. I think I tried baconreader and RIF along with Sync. I just liked Sync a bit better and have been using it since probably 2014 or so.