We waited very patiently for Revit to support 64 bit. I stalled buying a new laptop PC in order to make sure I had something that would support using a 64 operating system as well as having enough RAM to justify the switch. I settled on the Dell Precision M6300 a little over two years ago. Much to my annoyance Dell offered the same thing with 16GB of RAM just after I bought mine with a maximum of 8GB...a month later.
I find a wide range of conditions these days. People using 32 bit with 1 or 2 GB of RAM all the way up to people using PC's with 64 bit OS 24 GB of RAM, even a couple using servers for their workstation and even more impressive numbers.
Today The Revit Clinic shared a bit more (pun intended) insider information. I really enjoy this kind of post since it is both confirmation and confession. They provided this graph representing the evidence they obtained from the customer error reports and the customer involvement programs they have. You know those dialogs that appear after a crash that you don't always submit. You might consider a "cheeky" response like me.
Bottom line - 64 bit Operating Systems enjoy improved performance/stability over their 32 bit counterparts. If you haven't put some money and energy behind this move there is no time like the present.
While you are considering it...don't forget to replace the rear differential when you soup up the engine. I mean don't forget to put enough RAM in when you do make the switch to 64 bit. What's enough? In my opinion a 64 bit OS should have at least 8 GB of RAM. My next laptop will have as much as can be stuffed into it and I'll be hoping they don't double it again a month later.
Here's a link to a AUGI thread that might be worth your while too. Gordon has taken the time to put down (in a series of replies) what he's learned about how the operating system, RAM, virtual memory and paging files all play together.