Rated 4 out of 5 stars
I use this on four computers' installations of Firefox, all different in hardware, function, purpose, and use. However, there is a reason I use it on all 4: it works! Now, it is not a magic fix, and there are other Addon's that you can use to increase memory management effectiveness in FF, but if you had to pick just one, you could do a LOT worse than this!
Here are the computers I use on a day-to-day basis, and the before/after for each after having used MemFox for as much as ~10-12 months...
1) Laptop (QX9300 CPU @ 2.8Ghz, 8GB Corsair DDR2-1066 RAM, WD 640GB 7200RPM 2.5" HDD, Nvidia Discrete GPU, 17" 1920x1080p Display) - this is my "daily beater" laptop, and it was the first on which MemFox was installed... Average memory use went from ~1.2-1.8GB, as I typically have 12-25 tabs open at once, down to ~350-500MB!
2) Home Theater PC (AMD Phenom II X4 960T *unlocked all 6 cores* OC'd to 4.0Ghz, 8GB DDR3-1600 CL7, 2x120GB Intel 510 SSD's (RAID0), 4x2TB WD Caviar Black's (RAID0), 3x3TB WD Caviar Green (RAID0+HotBackup), LSI Hardware RAID Controller Card, ATI/AMD HD5890 2GB, 1x/ea 5.25-bay Blu-Ray Burner/Reader Drives, Lian-Li Case, 5x 120x38mm San-Ace 128cfm (1xExhaust/4xIntake), Corsair H100 "Liquid Cooling Unit" for CPU, 4x 120x38mm Scythe Ultra-Kaze 3kRPM/130cfm Fans (push/pull - venting out), HD-PVR PCI-E Card, Dual-Gigabit Ethernet NIC + Dual-Band Wireless-N 450+300 WiFi) - home theater PC, only the front shows with the rest behind the false wall in our basement Home Theater which is why I can use such heavy duty fans (HT room is sound-proofed)... Firefox uses ~82% LESS RAM on this computer with MemFox!!
3) Home Server (Intel Core i7 920, 24GB DDR3-1600 CL7, 2x180GB Corsair Force 3 SSD's (RAID0), 1x128GB Intel 510 SSD (Caching Drive), 4x600GB WD Velociraptor 10kRPM HDD's (RAID0), 7x2TB WD RE4 (RAID6), 4x3TB WD Caviar Green (RAID10 - in NAS Box via eSATA), 2x GTX460 SLI (F@H), Intel Hardware RAID Card (4xSAS = 16x SATA), multiple networking options, etc) - this stores over 14TB of data, and is accessible from my smartphone/laptop anywhere I have a data connection; that means that running Virtual Machines off of it is no problem, and thus I run Firefox directly off the Server; 78% improvement!
4) Workstation/Gaming Machine (i7 3930K @ 4.7Ghz, Rampage IV Extreme, 32GB DDR3-2133 CL8, 2x GTX670 4GB SLI, 2x Samsung 830 256GB SSD (RAID0), 2x WD RE4 1TB (RAID0), 2x WD Caviar Green 3TB (RAID1), External Blu-Ray Burner, Full Custom Liquid-Cooled Loop w/ 2x Pumps & 3x140mm/3x120mm/2x140mm Radiators(+lots more), viewed on 3x 27" (can't say brand) 2560x1600p 5ms IPS Monitors, full 7.2ch Sound w Definitive Technology & Klipsch Studio Monitor/Reference Speakers all-around and a Def-Tech Cube Subwoofer) - This, I really don't notice any tangible difference, but with that much memory @ that fast of a speed and low of latency, it's really not the fault of the program!
Overall, I couldn't be happier! I realize that Firefox has gotten its memory leak a bit more plugged up than before, but I still find this to be essential!!!