For about 5 years now my primary computer has been a Linux system based off of LFS. When I first compiled it, I was hesitant to go 64-bit, because LFS on it's own doesn't provide any directions for making a multilib system, and I knew I would need 32-bit libraries.
So, I made the decision to just go 32-bit. It made sense since I only had 4GB of RAM at the time anyway. I have seen the need for more over the years (running Firefox with multiple pages loaded and running a RAM-heavy game would sometimes bring the computer to a grinding halt), but it was still manageable. But I knew that I would probably eventually upgrade to 64-bit, especially when I could get a multilib setup. I put it off for a while, but two weeks ago I decided to bite the bullet and do it.