We have been using an access front end and SQL server backend for several years.  The program evolved from an Access front and backend application.  The performance across a WAN is terrible.  We moved to Citrix to keep the thing moving.  We are migrating to a .net frontend.  In the mean time you can use the Access database splitter to reconnect the Access frontend to the SQL backend.  Be prepared for occasional corruption in the Access appication.  Distribute only mde's.  Try not to go this way