Well, it's quite obvious that the text rendering is extremely slow in Carbon.
As an example the same test on Windows consumes at around 1%-2% of CPU (Intel Core(TM) 2CPU 2Ghz).
That's with ClearType enabled (ClearType acts pretty much the same as OSX default font anti-aliasing). Also, even if antialiasing is disabled for Carbon the CPU consumption is still higher.
Looking at the carbon code, I can see a lot of objects are being reallocated, so I'll try to improve the performance by caching some of them.
Another thing that **might** help is to rewrite the rendering engine, that's based on ATSU now (for OSX 10.4 compatibility) to CoreText. Both APIs are deprecated anyway with the whole Carbon. But ATSU is more deprecated