As some of you may have seen from the Basilica HDR post a few days back: I do like to play around with HDR photos. There are many tools out there but when it comes to open source software there is no way around luminance (formerly known as qtpfsgui). A number of people have asked me, since I am also using Photomatix Pro from time to time, how those two compare. I have prepared a photo album on flickr with some sample shots processed with both tools some time back. I try to update it from time to time but what you can see from the images in the album is that Photomatix tends to produce cleaner images with better noise performance BUT, and this really is a big but, there is a certain look that really seems to be only possible with luminance or more precisely with the Mantiuk tone mapping.
And last but not least some people say that the handling of luminance is more difficult than e.g. Photomatix. I can not agree because you need to have some practise with Photomatix too and Luminance did a lot of improvements recently. So in my opinion it comes down to the look you wish to achieve for your photos.