vncviewer in the unstable feed doesn't work with RC11 on my 860. This is because its looking for libstdc++.so.5, which is sadly absent. After some fiddling, my man scogan figured out how to get it working.
Make a temp folder to goof around in:
mkdir tmp
cd tmp
Get the RC9.1 version of libstdcxx:
wget http://mirror1.pdaxrom.org/rc9.1/feed/libstdcxx_5.0.5_armv5tel.ipk
It may be that you could simply use the package manager to install this ipk. We weren't sure that the package would install cleanly and not break stuff, so we extract the needed file manually.
Unpackage the IPK:
tar zxvpf libstdcxx_5.0.5_armv5tel.ipk
Now unpackage the data package contained therein:
tar zxvpf data.tar.gz
Now copy the relevant file into /usr/lib:
cp ./usr/lib/libstdc++.so.5.0.5 /usr/lib
Finally, symlink the file to its appropriate name:
ln -s /usr/lib/libstdc++.so.5.0.5 /usr/lib/libstdc++.so.5
Now vncviewer should work!