Should I migrate my whole file server to SharePoint as my sole document storage platform?
No, many files are not suitable for storing in a web-based format. Also, the infrastructure cost and admin cost of SharePoint is far greater than a file server. Only migrate documents that benefit from a managed, version controlled collaborative space. Identify active and non-active files and keep the non-active files on cheaper storage in file servers. Index them via the search and/or plug them seamlessly into the web experience using third party add-ons.