Think though, my 800mhz TiBook with the Mobility Radeon 7500 runs Leopard beautifully... It runs faster than my 1ghz eMac (probably because of the RAM but there you go)Max out RAM and give it CI capable graphics card. It should run 10.5 acceptably after that. Cheapest HW CI card should be flashed GF 5200 (if you can live with VGA-only - otherwise look for Dual DVI R9600 from G5 or GF 6200 to flash).
This CPU has 2MB L3 so it will perform like 1.0+ GHz one without L3. It can be OC'ed up to 1.0 GHz (voltage bump could be needed for 1.0) if you're handy in soldering.
Leopard shell run good on your mac i run leopard on a 733Mhz QS. i upgraded the video card to a GeForce4 MX and put a gig of ram in it and it runs finewell just picked up the quicksilver today ($40 craigs)
-ive just loaded tiger (will install leopard once i max ram out to 1.5)...im surprized how well this handles tiger...guess it's the 2mb L3 cache or geforce 2 mx...it runs better then my old imac 1.0 G4 that had 1.24 gig ram.
-? it's not overly loud...but is there way to make it slightly quieter? (ppc fan,exhaust fan and power fan)....it's very clean inside (no dust at all)....so thats not a issue.
-overall very happy with it (G4 867,896 sdram,120 gig hd) will upgrade ram to max,add a usb 2.0 pci card,...and find a good used lcd monitor for it's own.....