I've tested it extensively.
Playing music is loud. Pandora is loud. Ringer is loud.
Some video's are soft.
It's hit or miss but it's capable of being very loud. Especially listening to music or a ringtone.
I tested this, bringing in an Epic Touch , downloading an MP3 podcast on the ET and the GNex - did this with an Engadget podcast as well as a DMXS motocross Podcast - also a local radio station's podcast (these were all easy to pull down on the GNex).
In all cases the podcasts were super low on the GNex and I even played them back today with Mort Player on each phone (so that I was playing back the same file, same player).
If the GNex is loud enough for ya then great but for me , it's really low (ring tones, YouTube <which I played videos that I use as a std for testing volume>).
Some people could care less about the speaker for multimedia, claim to keep their phone always on vibrate or use headphones - in those cases, great, no matter the speak is very weak.
Between the speaker and the camera I'm very disappointed as i really wanted to purchase the GNex after waiting forever for VZW to get a decent phone - the Epic Touch (GS2) I really like - great camera, zero lag even with TW, I'm fine with the display <large, not super high rez> - if only VZW would offer a GS2 and would have done so MONTHS ago...
Now not sure what to do (as the Epic Touch - sprint is unbearably slow here). If only i could activate the ET on VZW ...... (3G speeds I'm fine with , decent 3G at 800 kbps or better). Sprint was like under 100 kbps.