I tried to give the 64-bit version a try, but I might have encountered a more general difficulties.
I tested this on Windows 7 Home Premium (Czech), the system is 64-bit (or I've hoped so sofar :-), according to System info: x64-based PC
I installed
Python 2.7 Windows X86-64 installer
from http://www.python.org/download/
which run ok, but the header in the python shell contains "win32"

Python 2.7 (r27:82525, Jul  4 2010, 07:43:08) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.

Consequently, after copying the respecitive files from issue2636-20101009.zip
I get an import error:

>>> import regex
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python_64bit_27\lib\regex.py", line 253, in <module>
    from _regex_core import *
  File "C:\Python_64bit_27\lib\_regex_core.py", line 53, in <module>
    import _regex
ImportError: DLL load failed: %1 nenÝ platnß aplikace typu Win32.

>>> 

(The last part of the message is a in Czech with broken diacritics:
 %1 is not a valid Win32 type application.)

Is there something I can do in this case? I'd think, the installer would refuse to install a 64-bit software on a 32-bit OS or 32-bit architecture, or am I missing something obvious from the naming peculiarities x64, 64bit etc.?
That being said, I probably don't need to use 64-bit version of python, obviously, it isn't a wide unicode build mentioned earlier, hence
>>> len(u"\U00010333") # is still: 
2
>>>
And I currently don't have special memory requirements, which might be better addressed on a 64-bit system.

If there is something I can do to test regex in this environment, please, let me know;
On the same machine the 32-version is ok:
Python 2.7 (r27:82525, Jul  4 2010, 09:01:59) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import regex
>>>

regards
   vbr