Oz Linden is very interested in having users update to a Server Side Appearance (SSA) capable viewer. He quoted stats (number and four zeros) of users still using older versions. When first reported the issue of a non-SSA capable viewer on an SSA enabled grid was that avatars would appear grey. In the past few days an issue was found where skin and eyes became corrupted and could not recovered while using a Phoenix viewer on an SSA enabled region. Details. LL is trying to find a solution but, that is likely a one-off effort and after launch they do not intend to give any time toward solving issues with the older viewers.
LL’s server side appearance blog announcement is here.
Kokua versions 3.5.1 forward are SSA capable.
Imprudence viewers are not yet SSA ready.
LL also announced the Materials Viewer is in beta. The blog post is here.
None of those features are Kokua. The code for the materials viewer just recently became public.
Comments about materials viewer and interest in having Kokua materials capable are welcome.