I have had brief contact with Cache with mixed results.
Yes, it was fast. I don't know if it is faster or slower than Oracle or SQL Server. Never did any performance tests.
The problem we had with Cache was the ODBC and the support for the ODBC. It was having lots of problems with Crystal Reports and VFP 6.0 and I was not very pleased with the support. It was eventually resolved but it took about 5-6 weeks to deduce the problem.

We are using Oracle with VFP and Cold Fusion as the front ends. Oracle is tops on my list right now for both support and performance.

Tom