There's a lot of reasons not to like autochdir as it messes up some plugins and if you end up doing :e ../../../foo.txt you are not gaining anything. Just as an idea try this cmap I knocked up
:cnoremap red edit <c-r>=expand("%:h")<cr>/
then you can type :red and get
:e /the/path/to/your/current/files/dir/
(edit: perhaps use z instead of red as there are commands that start with red)
To expand the topic, also check out the FuzzyFinder plugin and some custom mappings to rapidly jump to common files you are always editing. Eg
10 or so of your regular files should be no more than 2 keystrokes away. It helps if they are systematically named
Here's an idea I use for django.
http://code.djangoproject.com/wiki/UsingVimWithDjango#Mappings