I must admit that I’ve never been a big fan of the dash as /bin/sh change. I have three main problems with the switch:

POSIX compliance as an argument

Complying to standards is a really good thing. But when everybody is ignoring the standard because they want the comfort of newer features, maybe it’s a sign that the standard should be updated to include those newer features. Most of the bashims used everywhere in scripts were signifiant improvements, like the ability to write:

cp {short1/path1,short2/path2}/very/long/common/path/to/a/file

instead of:

cp short1/path1/very/long/common/path/to/a/file short2/path2/very/long/common/path/to/a/file

The option to improve bash was not fully explored

We started with the premise that bash is bloated, slow, and cannot be improved. Maybe you can help me with that, but I could only find a few simplistic benchmarks comparing dash and bash, and I could not find any analysis of why bash is slow, and why it cannot be improved.

One of the obvious problems is that bash is also an interactive shell, and is linked to ncurses and terminfo, which increases the startup time. But have we investigated the possibility to have a /bin/bash-non-interactive binary that would not be linked to ncurses?

The change was brought to users

While it is OK for Debian (or Ubuntu, in that case, since that change was done in Ubuntu first) to force its developers to use POSIX-compliant scripts, the switch could have been made only to Debian-created scripts (by switching them from a /bin/sh shebang to a /bin/dash shebang, for example). I have trouble justifying that this change was forced on users as well.

Next: linker changes

… and we are doing it again. A set of linker changes (see also the Ubuntu page) was already done in Ubuntu, and is very likely to be done in Debian as well. This switch requires deep changes in some buildsystems (it requires ordering of libraries and forbids indirect dependencies), and is rather painful (it was reverted before the Ubuntu 11.04 release because it was not possible to fix all the packages during the natty release cycle, but is done in the 11.10 release). Of course, there are justifications for this change. But I’m not sure that it’s worth all the trouble created for users.