By just starting Firefox and looking at the memory consumption, you are measuring exactly that: Consumption. Not leakage.
Leaking implies a continuously increasing memory usage. By just opening, measuring and closing again, you don't even get a chance to measure an increase in consumption, so you can't say anything about leakage.
Also, 100MB for Firebug, Adblock and LastPass doesn't seem that far off - especially Firebug is huge and has to do a lot of work, so I would expect that to require quite a bit of memory.
Good point and I will continue to monitor the browser as I use it. Just in initial browsing, I'm still finding the memory consumption increasing at the same alarming rate it was before sadly. :( But you are correct that I need to give it some time to really measure correctly.
That said, even with the 9 add-ons I'm using, I was hoping I could see a total memory usage on startup to be closer to 225MB.
Also having the lowest memory consumption is not always the best indicator for how good a browser is. For example, I think Chrome uses more memory per tab than most other browsers, because of its individual sandboxing system. But that seems to be a pretty fair trade-off. Has Firefox started using sandboxing yet?
Maybe you're right about lowest memory consumption, but what keeps me going back to Chrome is consistency in good performance and the fact that I can easily shut down one tab without having to restart the whole browser to reduce memory if that ever happens.
All browsers do have memory leaks but the fact that FF's memory continually increases to the point where I have to restart the whole browser every day is mentally tiring. This is where Chrome just got it right.
This was fixed for extension-free firefox. Today this is fixed, for extensions as well.
What was happening was that extensions had references to dom-nodes of a page, that prevented the page from being unloaded when you close the tab. Unless of course, the extendion author bothered to fix this from their side. Now, an extension has essentially "weak references" to dom nodes. (think: symlink)
I second this. On Ubuntu 12.04 Unity crashes after approximately 20 days of uptime and that's Almost the only time I restart Firefox. I regularly have a single session open for weeks.
Just to update, after a couple of hours playing with it, I am finally noticing it fluxuates up and down. It appears to let go of consumed memory after a period of inactivity. That's great news!
Glad to hear it! But as implied above, memory consumption is only interesting because of its effects on performance and stability (both of the browser and other programs running on the system). Don't choose your browser by looking at the memory consumption, choose your browser based on how it feels when you use it.
If you want to know what it's using memory for, hit about:memory.
This is also a useful way to start looking at a suspected leak: visit a page and hit about:memory to see what it's using, then close the tab and check about:memory again to see whether it's freeing everything.
Leaking implies a continuously increasing memory usage. By just opening, measuring and closing again, you don't even get a chance to measure an increase in consumption, so you can't say anything about leakage.
Also, 100MB for Firebug, Adblock and LastPass doesn't seem that far off - especially Firebug is huge and has to do a lot of work, so I would expect that to require quite a bit of memory.