So, I'm reading this wondering what I'm learning...
The OP was asking if Sonar X2 works with Windows 8 and the answer is a resounding Yes.
Whether it works measurably better remains in dispute, but there is at least one benchmark (performed by Cakewalk) which says it does.
http://blog.cakewalk.com/windows-8-a-benchmark-for-music-production-applications/ There are features specific to mother boards that can be set to make DAWs more efficient. BIOS settings, registry hacks and modifications to the Power Management within Windows are variously described to fix the issue of core parking for Windows 7. When I read the linked post and checked my Windows 8 PC, I couldn't find the core parking setting in Power Profile as described in the post. Perhaps because I'm using Windows 8 or perhaps my mother board doesn't support it. I only have a dual core.
Mad_Man has what appears to be a very knowledgeable post on the subject of core parking. Does anyone with Windows 8 see the "processor performance core parking min cores" parameter in their power options? I am not seeing it.
Next, John took offense at Alex's post and then vice versa. Couldn't you both have done this in Private Messages? I'm not sure why you did this in the public forum. IMHO, both of you could be speaking truth. Why you are fighting about it, I can't tell. Alex, we know John knew about the thread you posted on "core parking" because he posted on the same thread back when it was active. I don't want to speak for him, but if he announces it isn't an issue for him, I take him at his word. John, please don't be so quick to take offense. I didn't read Alex as trying to be offensive or dismissive.
Jim Roseberry, I think it's great that you took the time to try the demo project under both 7 and 8 on the same PC to compare. I totally believe that you are unable to see a difference with your eye. I wonder if it is possible to aggregate performance logging over time and sum the data. I don't know how to do this type of benchmarking off-hand, but it would be useful data.
Jim, you probably know this, but if you type PerfMon in the run window you can add specifically the SONARPDR process for logging.
http://stackoverflow.com/questions/69332/tracking-cpu-and-memory-usage-per-process Perhaps that would give measurable data which could be summed over time (the length of the demo song) to see if there is a measurable difference on your PC. This would take "eyeballing" out of the equation.