It’s quite normal for Firefox to be sucking up ~100 MB of memory right off the bat. We like keeping our apps running for a few days (that’s just the way we roll), and because of this, Firefox was using over ~800 MB of memory after about three days.
Firefox still uses a lot of memory – way too much memory for a web browser. If you thought it was too good to be true, you were right. One of the most significant “improvements” that Mozilla claims is Firefox memory usage, particularly the vanquishing of memory leaks. Firemin will eliminate all memory leaks in Firefox by tweaking the Rizonesoft Memory Booster core a little and applying it to Firefox, including extensions.