It's not hard to find decent SATA drive to PATA bus adapters. Whether or not some are flakey, plenty are just fine. I'm using several - one is on a PowerMac G4 with a 1 TB drive, another on a SCSI-IDE adapter with a 2 TB drive, and no problems with both long uptime, busy systems.
If you're worried about flakiness, just do some Googling.
BTW - only with really old drives does the lower speed of two devices on an IDE channel matter. On a modern system with a halfway recent drive (any DVD drive will be new enough), two devices will be clocked independently of each other, so one drive will only affect the other in terms of taking time away that could be used for transferring.
A simple example: if an IDE bus has two devices, one capable of UDMA-33 and the other UDMA-100, then a UDMA-33 bus transferring at 16 MB/sec would take half the time of the bus, leaving the UDMA-100 bus able to transfer up to 50 MB/sec. Usually this kind of contention doesn't create an issue on G4 class machines. On the other hand, a 16 MB/sec device communicating at 12 MB/sec will take 75% of the time leaving only 25 MB/sec on for the UDMA-100 bus.
Add to that some overhead, and you can see that there can be issues, but in most instances people don't use optical drives constantly, so it hardly matters, and even when they do use the optical drive, slowdown is often not significant.
If you're worried about flakiness, just do some Googling.
BTW - only with really old drives does the lower speed of two devices on an IDE channel matter. On a modern system with a halfway recent drive (any DVD drive will be new enough), two devices will be clocked independently of each other, so one drive will only affect the other in terms of taking time away that could be used for transferring.
A simple example: if an IDE bus has two devices, one capable of UDMA-33 and the other UDMA-100, then a UDMA-33 bus transferring at 16 MB/sec would take half the time of the bus, leaving the UDMA-100 bus able to transfer up to 50 MB/sec. Usually this kind of contention doesn't create an issue on G4 class machines. On the other hand, a 16 MB/sec device communicating at 12 MB/sec will take 75% of the time leaving only 25 MB/sec on for the UDMA-100 bus.
Add to that some overhead, and you can see that there can be issues, but in most instances people don't use optical drives constantly, so it hardly matters, and even when they do use the optical drive, slowdown is often not significant.