Rod Hagen informs me that Apple continues to post updated information on its Discussion Boards regarding the previously reported issue regarding blinking question mark problems at startup (caused by corruption of the startup partition) on some Alchemy-based Macs and Mac clones (such as Performa 6400 and 6500) after installing to Mac OS 8 (as also noted on MacInTouch). They now confirm that the problem is not limited to any one drive size or particular hard drive (such as a Quantum Fireball), as had been previously suggested. While not all users of these models will experience the problem, it is a serious one if you get it - as you will likely be unable to recover data from the damaged partition. As Apple has still not isolated the cause of the problem, the safest course may be not to update to Mac OS 8 until this gets worked out. Never turning off the computer (as the damage only occurs after a shutdown) is a (possibly risky) work-around.
Update: Scott Rogers reports that if he restarts his Mac and then immediately shuts down, he avoids the blinking ? that would otherwise occur following the shutdown.