I haven't seen major difference in uploading comparing 3.50 or the 3.51-snapshot(?) to 3.54. What has happened is that with 3.54 I have significantly less sequences that will not upload some photos at all.
I started (with 3.50) trying to upload 200+ sequences with a total of over 25k photos. That simply didn't work. Not with upload all, which often left nothign uploaded over night but was still processing only about 1/3 through the photos in the morning. Or then it had uploaded some photos of some sequences seemingly randomly. Same happened with uploading single sequences albeit I got to the upload part more often.
I then tried the 3.51-snapshot with seemingly no difference.
With 3.54 the difference is that with uploading single sequences the uploading gets done -- eventually.
But it requires many many manual uploads of single sequences. Which is not an option really. Not with hundreds of sequences. A major thing is that quite often only few dozen photos, sometimes less, and usually max around 200-300 photos at a time get uploaded. Even with optimistic scenario that would mean about 80 manual uploads with 25k photos. In practice more because many sequences are only some dozens of photos (due to problem with the distance-based capture).
I should also add that the app became reasonably responsive only after reducing the number of photos taken to less than 10k. And there's a big difference in the responsiveness at/below 5k, which is when it good.
All this has been mostly with Galaxy S7 and Huawei P10, so power of the device should not be the bottleneck.
To sum up my experience: The upload has become a bit better but not nearly good enough for larger amounts of photos.
Is there a way to make it possible to upload also photos taken with the app via the browser? I tried that but sequences in which the direction was set to be detected "facing forward" got only direction set "all north". Does the processing on the device do the calculation of the direction based on the .gpx in each sequence folder?
I look forward to seeing the upload work again soon -- as obviously all do.