Exactly this. It seems that people forget that no device is absolutely perfect and can have problems, even the beloved EVO 4G has had it's share of issues. The iPod touch 4th Gen had a few issues when it first released (I can vouch for this considering mine had a few before an OS update), iPhone 4, iPad, iPad 2, Xoom, the Toshiba Thrive had an update to fix a reboot issue, the Nexus One had a wifi problem before 2.2.1.
Another thing is, the Nexus S is pretty much a test phone for Gingerbread just like the ICS Nexus will be a test phone for Ice Cream Sandwich and the Nexus One was a test phone for Eclair. This is why the Nexus line gets an update before other phones, so Google can test it on their own hardware before other users get it.
Maybe the Nexus S can't handle 4G as well as Sprint and Google want it to. Does that make it a bad phone? No, it just means Google needs to work on it a little bit.