Well, to begin with, I'm using Visual Studio 2008 on a 32-bits Windows XP system. I have a second 32-bits Vista system but that's not used for development. I just ordered a new development computer which will use 64-bits Vista. (Don't want Windows 7 just yet, but will probably upgrade to Windows 7 in two years from now if it has a good market value.) (Btw, Intel Xeon Quadcore, 12 GB RAM, 1.3 TB diskspace over 2 disks.) I know that most 32-bits applications will work just fine, including VS and several others. I'm not too worried about this anyways. I also do development with Delphi 2007 but am not worried about this either. But I do want to take this in consideration:
On this new 64-bits system I can start developing 64-bits applications. This is new for me, so what are the most common pitfalls that I need to avoid when I start to develop new 64-bits applications? For example, datatypes that are of a different size, a file system that might be different, special 64-bits functions that I need to be aware of, possible conflict when I have to combine my 64-bits code with 32-bits assemblies, etc.
(I know one already: when developing web applications, I need to make sure my webhost is supporting 64-bits applications, else it's no use... Apparently, IIS doesn't seem to be able to support both 64-bits and 32-bits applications, so that's one pitfall.)
I'm not going to port 32-bits applications to 64-bits applications. I just want to create new 64-bits applications. From scratch! So without any 32-bits history. I've also read about this unanswered Caveat question but that's more about migrating. I won't migrate anything.