My background: have been editing on NLEs since 1996... back when footage was digitised at PAL or often half-PAL resolution off an S-VHS camcorder or VHS deck in real time through a very expensive PCI card. From there I've been through the first iterations of mini DV tape, Firewire and iMovie, several versions of Final Cut Pro, the first consumer Sony HDV cameras and the joys of authoring to DVD.
LumaFusion won me over as a fan due to it finding that oh-so-rare middle ground between the simplified, good-result-but-no-control-or-flexibility ideology of iMovie and its many imitators, and full blown NLEs that can do everything and the complexity that invariably goes with such applications.
The key to its success is simply this: it provides all the necessary editing tools and functions required to have proper, accurate control over the editing process, without trying to do 'too much'.
It both embraces the advantages of iOS's touch interface whilst being acutely aware of its limitations, and thus doesn't overwhelm the interface or the app with too many features that cannot be appropriately accommodated. It's a lean and mean, basic but professional editor.
I taught my girlfriend how to video edit using LumaFusion. Unlike me, she didn't have 20 years' prior experience in digital media, and wouldn't describe herself as particularly tech-savvy let alone familiar with the nuts and bolts of video production. Yet within a few days she was comfortably chopping up video clips and within a couple of weeks was producing YouTube-ready exports ready for upload. I think that speaks volumes as to how well LumaFusion works.
Its other advantage is the iOS/iPad platform itself. For me, being able to AirDrop over 4K H.265 video files straight off my iPhone and start cutting together without nary a dropped frame whilst out hiking, being away from home or even travelling in a car or bus is a huge time advantage. Doing a first rough cut while relaxing on the couch rather than being strapped to a desk is a joy.
Things have recently changed with my intended video work in the past few months, and along with it I've decided to add DaVinci Resolve Studio to the mix, in part to use the Speed Editor to see if I can literally speed up my editing process for certain types of videos (lots of cuts and not much else), and in part to improve my post graphics and effects with Fusion. Despite my previous experiences with Final Cut and Premiere, Resolve is again, a huge learning curve and a reminder of just how easy and straightforward LumaFusion is. It can't do everything, but for the basics it is just wonderfully efficient and lean.
I still see LumaFusion as a part of my overall workflow, especially as a super-portable, super convenient cut interface where rough edits can be completed away from the desktop, before XML-exporting over to the desktop NLE for further polishing and additional work.
Ironically enough, with the recent V3 update and upcoming feature packs a considerable number of more advanced features (multi cam sync editing, audio units, warp stabilisation) that might have forced some use cases towards a desktop NLE will now be covered within LumaFusion itself. The app won't and can never be all things to all people, but by golly it covers a lot of ground for most users
Whenever I hear "there aren't any pro apps for iPad", I just roll my eyes...