First things first, Geekbench can't run in Mac Os 9, so its results are not trusted for Mac Os 9 users. Second, it is very easy to fake Geekbench results: set the disk to check to a RAM disk and the overall system performance is increased.
Even I don't like the Geekbench results, let's take some of then that you have posted above:
PowerPC G3 (750GX) @ 1.1GHz
Integer Score: 804
Floating Point Score: 810
Memory Score: 242
PowerPC G4 (7455) @ 1.25 GHz
Integer Score: 888
Floating Point Score: 926
Memory Score: 549
The G3 results are what we can expect. There isn't a huge difference between a G3 and a G4. But the G4 can go further in to clock speed and overall system performance, plus Altivec and dual processors configurations...
I run OS 10.4.6 95% of the time, so for me it is a benchmark I can use. Am I happy with the performance I get, yes, especially since I only paid $50 bucks for the rig. It cost me more to pay for the shipping, I think $55 or $60. I agree with everybody here about the G4 and it's FPU and clock speed. For me, I wanted the fastest G3 I could get that runs Unreal Tournament and can boot into OSX.
I never turn the rig off, only re-boot into OS 9 to play UT, use my Adobe apps and ClarisWorks app for my MPG spreadsheet. I log all my vehicles gas purchases and mileage to figure per tank MPG, Cumulative MPG, Cumulative Cost, Cumulative Gals., Cumulative Miles, Continuous MPG, Fuel Cost/Mile, Miles Driven and discount savings on gas purchases.
Having a dependable rig is important to me. I don't have the time to "tweak" so this aftermarket cpu is perfect for my needs. Besides, I like the look of the G3 better than the G4 and it is color coordinated with my computer room.