Bye the way, having a local Castle is no biggy here in Scotland - they are everywhere :-)
Right, here are the originals, taken from -2 to +2 exposures:





And here is the finished article:

I used almost all of the sliders in the Photomatix Pro plug-in, but it is not necessary to do that, if you don't want to - good results can be had just by using the presets.
While this Castle is not the most photogenic, it does have some advantages - it is quite high, and it overlooks the village of Dundonald which, if you get it at the right angle and the right light, can look quite charming - but that's for another day :-)
So, does the 64 bit plug-in improve things for doing HDR from with-in Aperture? Well, Photomatix are going to hate me, but I didn't notice any vast improvement over the 32-bit plug-in. But what this plug-in does, it does well, and well enough to fit pretty much seamlessly into my Aperture workflow for HDR sessions. The resulting .tiff files are large, but Aperture just gulps them in and continues on with only a small pause in processing to indicate a larger than usual file.
The upgrade to 64-bit is free, the installation can be manual or via a supplied installer. All-in-all, this upgrade went smoothly, the plug-in worked flawlessly and the result was a smooth production of an HDR photo. Next time, I'll choose something a bit more photogenic!