I have been user of 64 bit OS since I got my new laptop with Windows Vienna a.k.a. Windows 7… though my lappy had only 4 gigs of Ram which was perfectly okay for 32 bit OS, I somehow felt that lets try 64 bit … 
and so I ended up with this machine. And I don’t have regret for this, but still sometimes I really feel annoyed ‘coz of some softwares …
I think, by making 64 bit browser MSFT has done really great job (yes… IE 8 is available in x64 version too…) … not even guys @ Mozilla ( beta 4 looks sexy though 
) which is really cool thing … because I don’t need to use x86 software for my x64 OS … anyways … I don’t feel annoyed because of browser, I am feeling annoyed because of add-on for that browser … that is FLASH Player !!! it’s really surprising that Adobe doesn’t support x64 flash player … perhaps the most downloaded add-on on internet … and the shocking thing is they are not even planning to make one soon 
!!! Just last week I was reading at CNET that Windows 7 is the highest numbered 64 bit OS sold in windows family. And I think this number is likely to grow large … and in this Web 2 era, we still don’t have even freaking flash working in x64 OS ??
(Image is from CNET)
Just today, something funny happened … I like to learn new stuffs by myself. I had installed DB2 DBMS few days ago, at that time I was trying to install an excellent software called IBM Data Studio which is basically neat interface to admin – develop DB2 but I always get error that I don’t have Java installed in my machine (Data Studio is based on Eclipse to it needs Java) but I know that I have already installed JDK 6 v18 … just now when I was writing this post about flash player problem, I realized that I have JDK 6 but its x64 not x86 
!!! Once I downloaded x86 JDK, I was finally able to install Data Studio without any trouble …
If you look at my Programs and Features, you will see redistributable VC++ for both architecture …
So from my experience of using 64 bit OS, if you have more than 4gigs RAM then you will feel the kick as 32 bit OS can’t use RAM more than 4gigs also you may feel difference in performance of some programs if they are specifically coded to gain advantage of 64 bit architecture … otherwise I think you may not “feel” difference … also, “most of” 32 bit software can be used in 64 bit environment without any problem …but some may not work well or even not run at all … and again, you need to have both x86 and x64 versions of supported software like .NET Framework … or Java …
It’s just a thought … 