Thunder is very nice but it's very slow to populate comments and posts to the point that it just skips through the comments. I'm trying to decide if I care about the whole sync data collection nonsense or if I want to use a FOSS app instead. I was also using Voyager and it was pretty good.
Edit: thunder doesn't seem to be updating my subscriptions automatically for my secondary account so that's a bummer. I was starting to slowly lean towards thunder as my primary app since it seems to be the smoothest UI experience outside of Sync. Voyager also has a really smooth UI, but it's not a dedicated app. Liftoff is my default at the moment. It just works.