Love Firefox III.
Been using the Gecko system way back in Netscape 4.1
I utilize about 54 add-ons. Now granted this slows Programs start-up, but it is a fair trade off for the add-ons that I use.
Load time is about 73 seconds.
Now over the years I have learned that there is little you can do about load time for Firefox.
My load time is delayed by a handful of my Add-ons, but I find that if I unload my add-ons or start Firefox in safe mode, the increase in load time is nominally faster by just a few seconds, approximately 14 seconds.
The load time for Firefox is incredible compared to any version of IE, Opera, or Safari so I have no complaints.
Now depending on how much bandwidth you have for an internet connection, I can speed up your specs well beyond the current specified Firefox spec's, and do so while being stable.
But as for load time we are stuck.
Now the biggest slow down to loading Firefox, or any web application, is monitoring software (ie, anti-virus, process watchers, Threatfire, nortons IS, AVG IS, Ad-Aware, Spybot S&D so on). The more of these running the slower the load time.
You want to see the load time on your browser reduced, shut down any Anti-virus or process monitoring software.
Now as for the Minimize to tray; there is a huge trade off for this little add-on. This allows FFIII to run in the background all the time, and if you set it up to run on boot, your computer takes longer to boot. You definitely do not want FF slowing down your system or slowly consuming your resources while sitting in your tray. Trust me on this one.
Realistically: there is no instant on. Only compromises.