Would It be worth it to upgrade to snow leopard?

to add to lemerise's comment about performance, just as point of reference here is some comparative benchmark data using Geekbench on a couple machines I still have with lower performance than your 1.12GHz G4:

1) PowerBook G3 "Pismo" 550MHz, 1.0GB RAM, OS X 10.4.11 (Tiger): Geekbench score = 375

2) PowerBook G4 12" 867MHz, 1.12GB RAM, OS X 10.5.8 (Leopard): Geekbench score = 310

both machines are slow by today's standard, but still useable for running MS Office, email, browsing the web. My son was even using the PB G4 recently to run InDesign CS3.

You'll note that the slower G3 running Tiger scores a bit higher than the faster G4 running Leopard. in practical terms I'd say they're both feel about the same speed (slow, but useable)

I would expect if you upgrade your iBook's RAM you might have marginally better level of performance than my PB G4 and as lemerise mentioned, a new fast hard drive will probably make a difference too.

one more comparison: my 3yr old MacBook Pro 2.33GHz Intel Core 2 Duo with 3GB RAM, OS 10.6.2 (Snow Leopard) scores about 3175 on Geekbench. so yes a completely differently level of performance on Intel vs these old G3/G4 processors.