I installed and used iPartition to redistribute space on my B&W G3 350Mhz (now 800Mhz) PowerMac. I too had an issue of a lack of space on my boot partition.

After downloading the software and retrieving the SW license key, I ran the Coriolis CDMaker SW (included with iPartition) to create the boot CD (you can't repartition a volume that is on the boot disk even if the boot is on a different partition.

I booted with the CD, redistributed my partitions to the desired sizes (took about 15-20 minutes with safe mode enabled), ran iDefrag Lite (included with iPartition) and rebooted my computer with the resized boot partition. PERFECT! results. Well worth the $45.00.