I'm thinking of installing a different spell checker, one that will run on JavaScript and check in-line as you type. However, Firefox 2 will have that integrated into their browser, thus I'm not sure if the spell checker will be needed.
Personally, I think I'm going to use Firefox's spell checker. I'm going to install Firefox 2 RC 3 this weekend and start testing it out. That way the speed of it is only based on my system, not SpellingCow.com and it won't require JavaScript (which some turn off).
I plan on using Firefox 2 so it will have the spell checker integrated.
Installed Firefox 2 RC 3, and this spell checker is pretty nice. Needs a little work on the algorithm, but that's fine. I'd rather have it built into the browser than use an external tool.