Newertech takes a different approach to designing CPU upgrade cards than do other manufacturers.  First, there is a bus timing issue with the G3 chip versus the 604e ROM chips.  There is a timing incompatibility (tighter tolerances in timing in association with predictive processing) with the G3 chip and the motherboard ROMs from earlier Macs that will cause some problems with backup software such as Retrospect, and incompatibilities with PCI upgrade cards such as the Adaptec SCSI accelerator cards, and possibly video cards.  Newer has addressed this issue by adding a hardware logic solution built into the upgrade cards intended for Macs with CPU daughter-cards.  The other manufacturers have either addressed this issue in a software fix, or have ignored or been unaware of this issue.  Thus causing some of the problems that I have seen with other G3 upgrades.  The problem with a software solution is that the fix does not come into effect until the software (usually an extension) loads.  Newer's solution is always in effect and there will be no incompatibilities due to this timing issue, or potential problems with conflicting extensions or other inits because there is no software to load.  This hardware solution costs Newer extra money and thus the cost is passed on to consumers resulting in cards that are a slightly more expensive than the competition, but their solution prevents you from running into any problems with Heisenberg.s Uncertainty Principle and I/O memory register accesses.  In other words system crashes, and data loss, and data corruption.  The second major difference between Newer and some of the other companies is that Newer does not support adjusting the CPU speed, but as discussed before this is not as big an issue for those who are interested in reliable performance that also happens to be extraordinarily fast.  (Especially those with investments in hardware that might be incompatible.)  I also suspect that not supporting CPU speed adjustments ultimately leads to lower support costs on Newer.s part, and fewer product returns.