I was initially upset about this, but I have to admit the Nexus S is fairly behind what most would consider modern smartphone hardware to be. Single core CPU, no GPU, barely any RAM to speak of, it's no surprise that Android has progressed to the point where it simply could not run well on such a device. Besides that, there is documentation available (though not widely advertised) that states that Nexus devices have an 18 month support lifecycle and the Nexus S hit that back in July.
I'll just have to accept my fate, and pick up a Nexus 4 when I'm able.
I'm fairly well-versed regarding ROMs, and actually ran CM and MIUI on it for quite a while with decent results, but that's not really the point. Nexus is supposed to mean "first in line for OTA updates", not "wait for us to put it on AOSP and then build and flash it yourself, or wait for a modder to make a decent ROM".
That is absolutely not the brand I thought I was buying.
Edit: Sorry, that was a ruder tone than I intended. I've got a bit of a love/hate relationship with my Nexus S due to the OTA frustrations, but I do love that Android has the option for taking matters into my own hands.
The tone's fine, it's not a great response to your frustrations. Carriers and phone vendors see additional support costs for no benefit. At the very least, Nexus does mean that you can get everything you need to build an image from Google directly.