While according to the status report also updated this morning, the number of P2 regressions has increased by thirteen, the number of less severe P3 regressions has dropped by seven. The number of the most severe P1 regressions remains at zero. For this release candidate that was just issued and the imminent 4.5.1 final release, the GCC development branch is currently frozen per this message.
The 4.5 release was significant for the GNU Compiler Collection in that it brought automatic parallelization support using Graphite, integration with the MPC library, enhanced support for the C++0x standard, optimizations for Intel Atom processors, and many other changes. Our GCC benchmarks and subsequent LLVM benchmarks with Clang have shown GCC 4.5 can also produce faster binaries, but with Mozilla Firefox for instance there were massive performance regressions -- hopefully they'll be at least partially addressed within the GCC 4.5.1 release.
As announced when releasing GCC 4.5.1 RC1, Richard hopes to put out the final release of 4.5.1 on or before the first of August.