I'm gonna try and justify one of these around summer time, not sure if I'll be able to do it though because my Nexus S already zips along Gingerbread, it's hard to imagine it being any faster.
Gives me till summer to see what competition comes out I spose!
Its not all about the speed though, over the Nexus S you gain -
A much better camera, much better video recording, a much better screen and then more power on top of that. Likely better battery life too.
What do you lose? Stock Android which is nice but mainly has little to no real benefits.
I dont know if the SGS2 has NFC, but do you even use that on your Nexus S?