I am one of those individuals who over the last couple years has been frustrated because of Oracle 10g will not run on 64bit Windows. I use a Oracle 10g Ex based program that was developed by a third party. It runs successfully on a ADM 64 bit system that runs Windows XP (not 64 bit Windows). All attempts to get it to run on Windows Vista or Windows 7 64 bit have failed. I seen on a separate post that the final version of 11g Ex is expected to run on 64 bit. Does that mean that any program that could used 10g Ex can now use 11g Ex.
Basically, I'd say yes. Some things changed a little bit from 10g to 11g, e.g. the case sensitive password handling, some parameters, etc., so there might be a few points to reconfigure in your applications... You might get a more precise answer if you outline which database features your applications use right now.