Yes, Firefox is fine. Awhile back it had a memory leak, but that has since been fixed. It can, however, get bogged down by add-ons, and it isn't as secure as Chrome. Firefox is also pushing Enrique to upgrade to version 12, but he thinks it's slow. Leo says he really has to keep up to date with browsers because of security concerns. The only reason Enrique didn't want to switch to Chrome is because of the add-ons he uses, but there are similar add-ons that he can use with Chrome.
Leo suggests trying the latest version of Firefox, and if it's too slow for him, he could switch to Chrome and find similar add-ons to what he was using with Firefox.