And foremost thank you for the great effort you put into PortableApps! I'm very proud to say I stuck with you long before my friends (who also keep switching to portable applications) or all the magazines around the world who are referring to you now.
I searched the whole site for this app that I'm requesting now, but couldn't find any information.
Firefox still is the most versatile browser, but the more intense usage you put into it, the more you will cripple it's performance. Unfortunately there are only nightly builds from Mozilla themselves with 64-bit support, but it will most likely never reach the end user (unless you agree to be an eternal alpha-tester).
However, I recently stumbled upon Waterfox (http://waterfoxproject.org/), that has since even been accepted by Mozilla.
I'm using version 9 that I made portable myself by copying the program-folder inside one from your portable Firefox installation. It runs smoothly and even after days and days of usage (with two dozen open tabs) a lot faster with a lot less RAM-usage (a constant 1.3 to 1.5 GB, whereas Firefox climbed up to 2.2 GB) than Firefox.
I was just wondering whether you would be interested to adopt this into your portable portfolio? I'm not a developer but not opposed to generate my own portable version with the means that I have, but maybe it would attract some more users. Both for Waterfox and PortableApps.
Thanks for your time and once again for your effort!