I've started playing around with Google Docs and Spreadsheets. Not much to report so far, except for the fact that it doesn't work with my version of Firefox. I quickly came to the conclusion, that this was probably due to the fact that I have the NoScript Add-On running, to protect me from all those happy-go-lucky "Let me just run this script on your computer without telling you" sites out there.
It turns out that the current "official" release of NoScript really does have problems with gDocs. Despite allowing all the various domains offered by the Add-On, gDocs still claims that JavaScript is disabled. Only when NoScript is disabled or all scripts are allowed globally, does gDocs work.
I then finally came across this post in the Mozillazine forums. It links to the current Beta version of NoScript. With the new (beta) version installed, Google Docs and Spreadsheets works fine.
Please note that, as usual, you should only run beta software on a test machine and back-up all critical data before installation. I will not be held responsible if this fouls up your machine and/or data.