Here are a few items you should be aware of
- contrary to ESRI's documentation, you need to do a very important piece of configuration on the client, namely add a reference to the service in the services file which is found (for most Windows users) at C:\WINDOWS\system32\drivers\etc\services. At the bottom add the following line (replacing servicename with the name of your sde service): service name serviceportnumber/tcp #ArcSDE for RDBMS
- make sure your server is listed in the pg_hba.conf file (in your postgres data folder)
- this entry must also be in the same file on the server, and also in C:\Program Files\ArcGIS\ArcSDE\pgexe\etc\services.sde, but that's usually less of a problem since the post-install takes care of it
- if you add your port number in the server field in the "connection properties" from your client (in my case arccatalog), it will return an error
- make sure your desktop software is the same major version as the sde (example: 9.3 to 9.3)
- http://forums.esri.com/Thread.asp?c=2&f=1717&t=142803
specified server. Entry for SDE instance not found in service file" ... note 1 above, particularly on the client side, fixed that