Q: Will This Device Work with USB 1.0?

Warren,

USB 2 will also talk to USB 1 devices but take four times as long or longer.  A firewire/USB enclosure will be the best option for new and old computers.

Jim~

Backward-compatible USB flash drives running at USB 1/1.1 speed (max. 12 Mbps or 1.5 MB/sec) don't have moving parts, but hard drives with rotating platters and moving read/write heads may suffer more because of the speed bottleneck.  USB 2.0 (max. 480 Mbps or 60 MB/sec) is 40x faster than USB 1/1.1, and the difference is noticeable when you look at the activity LED on a flash drive.  When connected to the slower USB bus, the light blinks, blinks, etc.  When connected to USB 2.0, the light flashes so quickly, that it's more of a flutter.  Depending on the amount of data to be transferred, an external FireWire enclosure for 3.5" HDDs - even if used as a temporary measure with the drive just sitting in it - would be so much faster, but more expensive than the USB/IDE adapter.  The adapter will work, but you mentioned "some G3 (and earlier) Macs."  If you're referring to earlier Macs with SCSI hard drives, that would change the scope of adapter hardware needed.

Warren,

In this post:

https://discussions.apple.com/message/11412346#11412346

you ask which one.  I bought this one and am happy with it for the price, not the speed.

Let's break your current question down to priorities.

"what would you say would be the best (and most cost-effective)"

Best and most cost-effective are contradictions.  To narrow down which is most important, consider the following.  We both indicated that Firewire is the best at transfer rates.  It is also the most expensive because Apple owns the rights to the name Firewire.  Other companies must pay royalties just to use that word on their packaging.

Transfer rates.  Speed is not everything.  When you see the estimated time to copy a group of files, hard drive features and other factors come into play.  I judge transfer rates this way.  When copying a hard drive, do I have time to go make a sandwich, go wash the car or go to town and buy groceries. 

Seriously, there is time to watch a movie while waiting for some file transfers.  But, so what?  If you are only doing the transfer one time, buy the cheapest option and go watch a movie.

"piece of equipment ..."   "hard drives on some G3 (and earlier) Macs I have laying around"

There is no one piece of equipment to do the job you described.

"connect the hard drives from the Macs I have"

Sounds like you have SCSI drives and IDE drives. 

"to either my iMac G4 or PowerBook G3?"

Pick one.  Most likely the iMac G4 so what ever you buy will be useful longer.  If the PB G3 has a Bronze keyboard, it will also have both SCSI and USB on the motherboard.  Pick that one instead.  You will need a special HD SCSI cable for that model.  That cable may not be easy to find.  Finding a Mac User Group would help.

The iMac G4 will be USB and Firewire with no option for SCSI.

If I'm not mistaken, I'm looking to copy data from the hard drives in an early iMac and a Mac-compatible desktop computer."

Have you considered connecting computers together in an ethernet network?  Here is one link:

http://support.apple.com/kb/HT1433?viewlocale=en_US

Another popular site is car1son.

"I'm looking to copy data from the hard drives in an early iMac and a Mac-compatible desktop computer."

The early iMac will have an IDE drive and the Mac compatible will most likely have an IDE drive because they were cheaper.

As you can see, your question was not as simple as you thought.  Go with the ten dollar ebay adapter.  If you find it too limiting or you need SCSI or more speed, plan on spending more time and money finding additional options.

Jim~