I have to correct myself here.
You can not have ultra high setting with software mode.
I noticed some other differences:
I don't have 5.1 sound in software anymore
Only stereo.
With hardware sound, there was kind of a low-pass filter applied to the sounds, what sounded quite good. The disatvantage was that the hearing distance was shorter. But I am not sure if the not so muffled distant sounds are because of the new sounds in 2.25 or because of the change from hardware to software mode.
A wild guess of me is that software mode does not apply all/any? of the computations (filter) to the sounds.
Afaik the rain effect is placed a lot of times on the map. Is it possible that each of these effect areas plays a rain sound and that all of them played together overcharge the soundcard which can only compute 128 voices at a time? If that is true one could delete the sound of the effect and replace it by one global rain sound.
I miss my surround sound so much
!! PLEASE fix this.
Edit:
With more computing power with multiple core processors, software might be the way to go...? I'm confused.
Hm I doubt that the sound is computed on another core in BF2, but the cores got faster too since the game was released.