For customers migrating from jrockit, not enabling tiered compilation by default leads to a number of regressions:

1) For fusion apps, tiered compliation yields a large benefit (assuming we have adequate code cache). This is because fa are large, and so have a long warm up cycle before everything gets compiled, but also because there ends up being code that never gets compiled because it is called too infrequently.

2) For quick-runing programs using a 64-bit JVM, the early compilation by jrockit enables them to run much faster.