I posted my Nexus S first impressions last week and after several more days of usage I have to say I don't see anything in this device that would ever have me buying it over other Sprint Android devices. Actually, I have not seen very good battery life and signal strength has been very questionable.
A few readers sent me emails after my first impressions article stating that they purchased the Nexus S and had nothing but problems with the 4G and 3G signals, even after trying out several Nexus S devices. I found many comments on the Sprint and Android Central forums, as well as on other Android enthusiast websites. I know most of the time people with issues are the ones who post on forums, but the number of comments is quite high for a device just one week old.
I had a Sprint HTC EVO 4G for about 7 months and experienced excellent signal strength and connectivity in Seattle and other areas. In these same areas, I am seeing quite poor connectivity with the Nexus S and finding that WiMAX is barely a usable feature in the device. I don't know if this is a Gingerbread issue or a Samsung hardware issue, but I have read that the T-Mobile Nexus S is not the strongest at maintaining a signal either.
While it is nice to have a device with pure Google, unless you need to have a full featured Exchange experience, signal strength is much more important than this experience. I would personally consider waiting for the EVO 3D or getting something like the Epic 4G if you are looking for a Sprint 4G device at this time.