Moving from MSSQL Standard to MSSQL Express Most of our clients run our program with MSSQL Express as the back end

Some of our clients had to purchase MSSQL Standard when there database got past the 10Gb limit of MSSQL Express. Using Filestream we were able to shrink the DB Sizes below the 10Gb limit and are now transitioning the clients back to MSSQL Express to prevent the customer from having to pay for updating there MSSQL (2008 to new version)

My question is, are there any issues that I need to be aware of that can cause (Mostly performance) issues?  


Client DB's are +-150Gig with one table (with attachments) taking up the bulk of that.   


I am especially cautious of the Memory limit of MSSQL Express?