Taking the step from 32-bit to 64-bit has been much more difficult than many had anticipated and has been in the workings for close to a decade - compare that to the relatively quick transition from 16-bit to 32-bit in the mid 1990s. Of course, there are hurdles that need to be overcome and the benefits of a 64-bit app are only now becoming much more mainstream with more vendors now motivated to think about a transition.
Mozilla's product manager, Asa Dotzler, just posted a somewhat careful question to the Firefox community and asked users what they would expect from a 64-bit version. The question by itself may be confusing as the perception of a technology may not be aligned with its potential. However, Dotzler's post indicates that very little research has been done on Mozilla's side to figure out what the opportunities of a 64-bit Firefox really are as he tells his blog readers that "any help is appreciated."
Of course, Mozilla has done some research and was out quite early with a 64-bit version of Firefox. Firefox 3.1 was the first 64-bit version of Firefox and was released in fall of 2008. "Released" is an overstatement as Windows Firefox 64-bit builds have never made it past the developer channel and are even today only offered via a nightly build download (now in version 8.0). Last week, Mozilla announced much more serious test builds of Windows 64-bit builds as it installed Windows 2008 servers "that can generate the 64-bit version of Mozilla Firefox."
So my questions to you would be: Do you care? Are you waiting for a 64-bit Firefox?
My general notion is that most of us don't as we haven't really run into any problems with 32-bit yet and the benefits of 64-bit are not that obvious. I may be wrong.
Obviously, caring for 64-bit (and caring more about it than just perceiving the greater number as a bragging right) still requires quite a bit of understanding for the technology. 64-bit hardware has been available since 2003 from AMD and since 2005 from Intel, indicating that you most likely run a PC that supports the basic feature set for running 64-bit software and can go beyond the physical memory limit of 4 GB in 32-bit systems. The main benefit of such software is that it can process data in larger chunks and can distribute more memory between the OS and applications.
For example, Windows XP (32-bit) had an addressable limit of 2 GB, while the 64-bit version offered 128 GB. Windows Vista 32-bit had a 4 GB limit, while the various 64-bit versions went from 8 to 128 GB. Windows 7 32-bit has the same 4 GB limit, but its 64-bit versions now support up to 8 (Basic), 16 (Premium), or 192 GB (Professional and up). Microsoft's Windows Server 2008 R2 goes up to 2 TB in Enterprise and datacenter editions. So, provided that you have more physical memory installed than those 4 GB, there is the potential of performance increases, especially if you tend to work with many tabs and memory intensive applications.
A problem area are also plug-ins and add-ons that are not available in 64-bit - which include Flash and Java. Adobe neglected Flash 64-bit for quite a while and just announced last week that there will be a renewed effort to take Flash to 64-bit with version 11. Vast areas of the 64-bit landscape appear to still be a chicken-and-egg scenario, especially as far as browsers are concerned at this time. Unless all components are in place, it is unlikely that many users will switch. Given the fact that Mozilla is just now pitching about a transition, I would think that it is not time for the user to be concerned yet.
According to Dotzler's post, 64-bit's main problems appear to be the general education problem on what 64-bit really is, plug-in availability and the general memory footprint of Firefox 64-bit, which is higher than the footprint of the 32-bit version. Dotzler does not consider these issues as deal-breakers, and also hints that performance increases and better security features may be possible. He noted that he wants to have all the pros and cons figured out this summer or fall, which put a Firefox 64 into the early 2012 time frame?