I am loving the Nexus S. Very sweet phone, and seems like it does a far better job finding a data signal han my Evo. And it's fast. There's a few little problems like the volume being a little lower than my evo, but there's one thing I can't seem to fix - the voice mail notification icon. How do I clear that? it's been up every since I programmed my phone and got it activated.
The way I have done it on the Nexus and the Evo after the GB update is to call from another phone and leave me a voicemail, listen to the new voicemail and delete after finished. This has always cleared the voicemail icon on my phones. Hope this helps.
In regards to the low volume, I have been using Volume+ on my Nexus, it increases the media and alarms volume to an acceptable level with little distortion. Have not found any difference in ringtone/notification volumes but speakerphone volume seems better. Using a volume boost of 5-6 db seems to work best on my phone. No ill-effects so far that I can see.
I bought the full app, but they recently released a free version so you may want to give it a try.