What are common drawbacks, gotchas, and problems of choosing Vista 64-bit versus 32 bit? We recently purchased two laptops and selected Vista 64 bit, but I'm considering downgrading to Vista 32 bit on both. The only reason for going 64 bit was to get access to the additional RAM.
Obvious issues include that many drivers only come in 32 bit versions which won't run in 64 bit Vista. Less obvious is that ODBC drivers are also drivers - they can be accessed using a 32 bit ODBC manager included in Vista 64 bit. Some programs which run fine under the WOW (Windows 32 bit on Windows 64 bit) environment include 32 bit printer drivers to facilitate for example printing to PDF. That doesn't work so fine.
What else is there?
I guess this is just another example of your 'obvious issue' but the Cisco VPN clients we use do not work on 64bit.
You'll continue to run into issues with 64-bit for now (until more app vendors create x64 apps), unless you use a small set of applications that for sure work in a 64 bit environment.
For example, my desktop is Vista x32 because I have tons of programs that I need for various projects.
On my laptop, though, I usually just use MS Office and IE, so Windows 7 x64 has worked fine for that.
So my bottom line advice is to stick with x32 unless you run a limited set of applications that work in x64.
Running 32bit applications on a 64bit operating system allocates larger blocks of memory than needed. It's probably not noticeable by an average user with MS Word and Outlook open all day, but for heavy load systems it could be quite a difference.
Other drawbacks I've seen at our company is 32bit applications having troubles intergrating with the explorer interface (like the right-click context menu on files).
Right now my best advice is to stay on 32bit on desktops unless you actually need it. Servers is another ball-game, 64bit there usually only comes with sunny days.
On the bright side: 64bit desktop OS is fabolous for CAD users, heavy 3D modeling users etc.
64 bit is the way to go. Running a 32-bit OS today on modern processors is like buying a mansion and living in the closet. The biggest drawback to vista 64 is running 32 bit apps that expect a 32-bit OS to run on. Vista 64 will run any 32-bit app but it uses Windows on Windows to do so. The systemroot is different under WOW to ensure that a 32-bit app does not call any native 64 bit OS dlls. You will need to do some testing to verify that any quirks don't appear, but by and large users are quite happy at seeing the same hardware that ram 32-bit xp or vista, show a dramatic speed increase just by going to 64 bit.