I recently launched a B2B platform that required a VPN connection to each of my customers back end server running a proprietary software package on top of MSSQL. In order for my app server to have access to the client MSSQL server which was on a different computer than the VPN server itself I needed the advanced routing on AWS VPC ...

EC2 was enough for me to prototype my system to get 2 clients on board, but I needed VPC to accomplish the multiple VPN connections that I use ...

Also, my storage servers have no need to be addressable by my clients and/or the Internet at large. So while I could have done that with security groups, having them in a private subnet made things much easier ... and now I know that from an IP level the file storage cannot be found from outside of my VPC.

I'm sure if I sat down and thought about it I would come up with more ...