After installing the latest RM debugging process takes a lot of time.
Before each breakpoint I placed IDE hangs for about 3-15 seconds. Then it displays current vars values via inline debugging. If I choose "Step over" after that it is repeated again. It is almost impossible to use such kind of debugging I think.
But I don't have any performance problems with Idea 14 installed while using inline debugging.
OS X 10.10.1