Might be just the placebo effect, but my initial impression of the update is the following. Everyone has different hearing and different hearing aid settings so my impressions are relative to what things sounded like to me under the original firmware with no change by me of my previous settings.
I hear a bit more high frequency sound. Sounds seem a bit cleaner and crisper, including speech. Because I wear a very occlusive fit (cShells with no vent to facilitate noise removal), my voice with the previous firmware not only sounded boomy in the base range but the overall sound of my voice seemed a bit suppressed (and I would overcompensate by speaking loudly). My voice is still occluded but sounds more natural to me after the update, giving me a better sense of the volume I’m speaking at. I have an improved sense of sound localization, too; my brain seems to be telling me much more decisively than before that sound is coming from a particular direction.
It would be nice if the firmware update made Spheric noise reduction come on automatically more readily. With the previous firmware, it took a really noisy place, like an Apple Store full of customers, to trigger Spheric noise reduction.