Since the release of the unofficial firmware update we are able to give the apodizing filter a spin, so I tested it thoroughly myself earlier this year. Still I have not the feeling that the majority of Meridian owners have done this themselves. The general consensus is that the apodizing filter is superior to the old filter, but this is usually based on experiences with new devices that contain the new filter by design.
My own experience with the apodizing filter: the advantages are pretty clear from the start, pin point imaging and spacious at the same time. Unfortunately I also noticed some disadvantages. The main problem is that I got a feeling of pressure on my ears which made listening uncomfortable. Also I found the sound to be dull or boring, and I ended up playing 6dB louder than I am used to. I suspect the pressure on my ears killed the highs, so I compensated for that. Another remarkable issue was that the sound was not natural when being not in the sweet spot, for instance when I was just walking through the room. A final remark is that I found the bass to be pronounced too much, this also adds to the unnatural feeling the filter gives.
Switching back to the old filter removed the problems of the disadvantages, and in my case is the preferable solution. I am glad that I have the option to choose myself which filter I want to use, instead of being forced by Meridian. This also means I won’t (can’t) buy a new device, since I would be stuck with the new filter.