I take a ton of photos on my iPhone, and I've always tried to keep my workflow as simple as possible: no multiple app import/export shenanigans. For a long while I was using the original VSCO Cam app—I loved the filters but wasn't a fan of the slowness. Afterlight (formerly Afterglow) came along and solved a lot of the problems I had with VSCO's interface, even if the filters weren't as great (I value convenience highly when using my phone!).
So you can imagine I was pretty impressed when the new VSCO Cam launched a couple of weeks ago; alongside a whole raft of new filters, a much improved UI (with a few quirks) and significantly better performance. Note that if you're going to buy any of the preset packs, it currently makes a lot of sense to cough up $5.99 for all 48 presets. Given that the app itself costs nothing, it's money well invested.
I've been using it non-stop since I got it. Most of the below use the "F" and "K" presets, which are easily my favorites so far for their relatively muted look.