/etc/skel/.profile should be strictly sh

Binary package hint: bash

According to the bash manual page, e.g. tilde expansion is a feature which is absent from "Bourne classic" sh.

Since $HOME/.profile is potentially read by other shells than Bash, it should probably only use the strict Bourne features.

Perhaps the comment near the top should include a remark about this, too?

I would suggest at least the following change:

 # set PATH so it includes user's private bin if it exists
-if [ -d ~/bin ] ; then
- PATH=~/bin:"${PATH}"
+if [ -d ${HOME}/bin ] ; then
+ PATH=${HOME}/bin:"${PATH}"
 fi

For consistency, you might want to perform a similar substitution in the preceding stanza where .bashrc is loaded if present, although that is of course technically only ever evaluated by Bash if the logic works correctly.

Especially in mixed environments, where users' home directories may be NFS-mounted on a number of different architectures, avoiding compatibility problems in the default .profile is probably a good idea, and should help lower the threshold for large organizations to accept Ubuntu.