Interesting thread. I need to check whether I have this Nik Dfine software as I have a suite but I am currently using parts of it only. I installed CS5 and noticed that it does not support the Nik plug-ins which is a bit of a bummer as obviously Nik is so much more then just noise reduction (as you can tell I did not even know they have it until I read this thread).
I saw some HDR results produced by CS5 and it looks rather promising. Not that I am a too big HDR fan but at times where the dynamic range is too high it is either using multiple layers or HDR merge. Until CS4 the HDR tool is unpredictive and requires alot of manual work. Photomatix is a total turn-off.
So, all and all need to have a closer look at CS5 as I have some noise problems on low ISO shots, due to long shutterspeeds making the noise kick in.