If you're seeing a lot of disk writes, then you're either paging the program out or you are writing to the disk cache. Paging would be a symptom of not a lot of memory or Windows being too aggressive in page stealing.
I run without a pagefile on my systems (they typically have 1 GB of memory though I'm thinking of going to 1.5 on my K8). If you think it's a disk cache issue, turn off the disk cache and see if the writes go down.
I used to run without a disk cache but with a large memory cache but am back to using a disk cache now. It depends on your relative network speed as to which performs better.
Why optimize Firefox? I have a lot of photos that I've taken with a digital camera that are typically one MB and my performance benchmark is that they take a second or less to render. I like pages to come up in one to three seconds and like a fast startup time as well.
Firefox as a ton of tuning prefs that are exposed through the about:config interface.
I like a lot of convenience extensions as well and these slow the browser down so speeding it back up with code optimizations makes the extensions free.
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