I too was a SiteAdvisor user, namely Firefox plugin user, until yesterday when I allowed it to update, after which I found out it had installed more than I had asked for w/o asking for permission. (Later I found out it had broken IE7 apparently.)
It seems the days of standalone Firefox plugin are over, as the current installer available installs this new monster (IE/Firefox plugins + System service), user has no choice any more.
You should give WOT a try happy Devs are responsive there and their plugin is just plugin. Staff there participates actively in the forums, which is a nice bonus.
Wow, just upgraded Site Advisor to the version in question - and just as quickly removed it.
Thanks for the heads-up about the service it adds to the system. Funny I didn't notice that. Maybe it's because it wasn't mentioned in the install! This is appalling behavior from a so-called anti-virus company. Since when does installing a firefox add-on mean automatically adding a service to your machine and an add-on to IE as well? *cough* *cough* Drive-by download *cough* *cough*.
I've used SiteAdvisor since before it was bought by McAfee, but I don't trust it anymore. Why would I rely on site ratings from a company that is this fast and loose with their own site? Pass.
As suggested in this thread, I installed WOT instead. Strangely enough, they only installed an add-on into my Firefox. Not IE. No magically appearing services on my system.
Goodbye SiteAdvisor, it's been fun. Thankfully, I don't rely on McAfee for my virus or antispyware protection.