SQL Server Compact - Will it perform well with heavier traffic sites?
I have not used SQL Server Compact, but because of its design, there are warnings in the SQL Server 2012 documentation about concurrency issues.

See: http://technet.microsoft.com/en-us/library/ms171845(v=sql.110).aspx  for warnings on:


Lost updates.
Inconsistent analysis (nonrepeatable reads).
Phantom reads.


If you need a free and much more functional version of SQL Server, consider using SQL Server Express.  Its limits are considerable above the Compact edition.  You can lookup its limitations.