I have been very pleased with FF4 so far. A few of my plug-ins no longer work but that's to be expected. It's a nice looking, quick browser that still uses more memory than I would like but I suppose that's why we all have 4GB+ of memory on our machines.
"It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring."
- Carl Sagan
Intel i7-5960X | ASUS X99-Deluxe | 16GB Crucial DDR4 | Intel 730 240GB SSD | Crucial M4 256GB SSD
WD 1TB Black x1 | 2 x EVGA 770 GTX Superclocked SLI | Corsair H110 Water Cooler
Corsair 750D | Windows 8.1 x64 | Dell 2410 x 3 @ 5760x1200
Intel i5 3570 | ASRock Pro4-M | 24GB Patriot DDR3 | WD 250GB | QNAP NAS iSCSI Shared Storage