The other main argument is that hardware is now dynamic.
Here is very common hardware:
* USB headphones with microphones
* USB sound card
* Bluetooth heaphones
Notice how they are all dynamic?
So yeah. Alsa, by itself, can work really well if all you want to do is listen to Flac files over a static configuration... but it's shit if you want to do anything more complicated like:
* play more then one sound simultaneously (I'd like to see you program into your asoundrc file a audio mixer that does not suck)
* use your microphone
* use audio input with more then one application
* Use X11 applications over a network that have audio
* use a USB docking station for your laptop
* use your bluetooth headset
* Be able to switch your bluetooth headset between stereo sound and telephone modes
* configure your laptop's audio output (on the fly) between:
- off
- stereo audio with input
- 4 speaker surround sound
- stereo audio with digital output
- digital output with digital input
* Play your game's audio out through the speakers and then chat with people on your usb headset
And a bunch of other crap people using other OSes take for granted but is nearly impossible to do in Linux with any sort of sanity and when it does works it only works in extremely static and carefully maintained configuration.
And, no, switching to OSS is not going to help any since OSS, even in the newest versions, is less capable and more of a pain in the ass to configure then Alsa is... OH it uses software mixing by default, unlike ancient versions of Alsa. One problem solved and sixty thousand more to go.