Well, all I can say is, it's what you need. I got the 1 Ghz model customized with a SuperDrive, mainly because I didn't need the 80 GB HD (I have external drives, which are much faster than internal laptop HDs for movie-editing

, AirPort Extreme, and backlit keyboard (I can type without looking at the keyboard, and Apple doesn't have an option for taking the backlit keyboard off the 1.25 Ghz model). But otherwise, the 1 Ghz model just was great for me.
Before, I was going to purchase the 12-inch model, but realized that it was a better value to get the 15-inch model, because you get a much better LCD screen, faster memory/bus speed, FireWire 800, PC Card Slot, Gigabit Ethernet, 60 GB HD, etc. Also it was about a $200 difference with an education discount. Not a bad value at all.
When I got my computer, I was totally satisfied with it. It had the speed, snappy-ness, and slick looks. No matter which model you get, you'll be satisfied with it. Since I customized it with a SuperDrive, it was comparable to the 1.25 Ghz model, besides the AirPort Extreme and 250 Mhz difference between the two models. But once you think about it, comparing the previous TiBook model with the new 1 Ghz Aluminum PowerBook, the new model is slightly faster because of the faster L2 cache, bus speed, etc. So I've always thought about it that way.
It all comes down to this question: what exactly are you going to use your computer for? If your going to use it for pro apps, then I guess going for the 1.25 Ghz model would be better. Otherwise, I still think the 1 Ghz model is a great value; you'd only wait a few more seconds for finishing some tasks. Either way, you'll be satisfied. I use my PowerBook for movie-editing, After Effects/Photoshop work, etc. But remember this: RAM always speeds up your computer. I recently added a 512 MB stick, all adding up to 768 MB for my computer now. So I'm happy.
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Power Mac G4 Sawtooth 450 Mhz, 1 MB L2 Cache, 640 MB RAM
iBook G3 12-inch 600 Mhz, 256K L2Cache, 384 MB RAM
PowerBook G4 15-inch 1 Ghz, 512K L2 Cache, 768 MB RAM
Apple KICKS ASS!