RequestPolicy and other tools like HTTPS Switchboard or even Ghostery let you block all content from certain domains, not just JS. They won't even load a tracking pixel. RP is whitelist-based and it can take some time to enable all the domains you actually use. Ghostery is blacklist-based and targets known tracking domains.
Thanks a lot for porting uMatrix to Firefox. I've been waiting for this since the first time I used HTTPSwitchboard for Chrome!
I run Ghostery as well, but I learned something new, never heard of tracking pixels. I've added RequestPolicy to my suite!
Ghostery should be blocking that sort of content (that's the point), but I really like NoScript and RequestPolicy in conjunction with each other for the control it gives me. Configure firefox to ask to allow flash, and you've got a pretty complete privacy toolset.