Well, I gave it an honest try. I ran the 64-bit version of Ubuntu 7.10 for a good long while. Truth be told, I liked it quite a bit. But, I've gone back and installed the 32-bit operating system on my AMD64 machine at work.
First off, let me explain why you should care about 64-bit versus 32-bit. In the future, not to long from now, there will only be 64-bit computers coming out of the major vendors. Intel and AMD both have roadmaps leaving the 32-bit architecture in the dust. Not only because of the higher memory limits, but because of other architectural improvements that the addition of an extra 32-bits of data has allowed. In fact, many benchmarks show a speed difference in actual work favoring the 64-bit CPUs. One such example is encoding MP3's a few seconds faster, which pretty much everyone can appreciate.
So why would I stop using a platform that better takes advantage of my new hardware? In a word, software. Software is the final sticking point for most users and computer vendors. While most software can easily be recompiled for the 64-bit platform, few packages take true advantage of it. In addition, some packages do not support it at all! This lack of support from very few software vendors makes my life difficult- and I refuse to make Linux difficult.
This post is a cry out to the authors of Flash, and the men and women working at Google writing their browser extensions and web apps. Support 64-bit platforms! You will soon be left without a choice, and there are already tons of people out there using such software. Or, better yet, if the people writing Gnash (an open source alternative to Adobe's closed source Flash player) crank out improvements in the next six months, most Linux distributions will pick them up for their next release cycle.
In 2007, the 64-bit architecture isn't new. We've had PowerPC chips. SPARC chips, Alpha chips, and the list goes on. Most of these have been around since the 1990's, and are very well supported. This means there has been about a decade at least to develop software support for the 64-bit architectures. And yet, support is still lacking. There's just no excuse for that anymore.