I vote for keeping icos as they're right now. I don't see any benefit in changing them at this point.
I don't see why the proponents of this idea try to impose Tango icons over default ones when going from one icon set to another is a namechange away. Another concern is that some people here seems to assume that users thing current ones look "unprofessional" or that everyone needs "unification" or that many people will like the Tango ones just because they follow some guidelines or are the same color, etc. I disagree with everything above. First we don't know what is the profile of the average Inkscape user so we don't know if he likes tango, if he prefers one shade over differentiated colors, if he uses other apps like Gimp or Scribus (personal opinion: i use Inky and Indesign and Photoshop)... Hell, we don't even know what is the majority operating systems of these users, which brings me the following point: what is "unification"? Keep in mind that not everyone uses Tango icons, not everyone uses gnome, and not everyone uses even Linux! What about users in Windows or MacOS?? This won't bring any unification for them for the most part unless they have Gimp or Scribus (maybe other apps), and not everyone is using them with Inkscape. So what's the deal? Also about the point of icons being made of a single color vs. multiple colors... well, maybe is matter of taste, but i like icons to be distinctive in shape and colors. A single shade of a color won't make them inherently "better", rather the contrary (IMHO). Adobe has done that (single color icons with minimum saturation) and is a hit-and-miss approach. In one hand they won't distract the user, on the other difficulties on picking and telling apart tools might arise (i'm talking about experience).
I could agree that the current icons could use some improvements here and there but bashing them and sustituting them just based on those arguments seems a bit unfair to me. Why we don't try to see what current icons are worth for and improve from that? or improve the Preferences dialog to let the user choose easily between icons sets? As english say "don't throw the baby with the bathwater".
Well, that's my opinion ;)