SharePoint 2010 : First custom connector implementation for BCS

Today, I managed to read on BCS a bit and wanted to try out some custom connector implementation for the external systems.
Found out this code snippet from MSDN for a connector to the file system.
Managed to complete this exercise and created an external list with the External Content Type and I did see the files from the file system in the list.See bellow images.
Folder contents in file system :

External list in SP context :

I am really impressed by this and it has already inspired me to go deep into this and hoping to create some more custom connectors for other external systems as well.
Found out lot of issues/problems while I am doing this and I just list down possible erroneous  scenarios.

1. Business Data Connectivity Services issues
2. Assembly deployment to the GAC
3. Assembly information
4. Configure Business Data Connectivity access rights

Keep those things in mind if you also get into trouble.