Mac Pro 2013 Article Roundup
The new Mac Pro has already seen a ton of reviews and information. Here is a collection of a few great links.
Probably the best technical review from AnandTech. For a less geeky review, there is a good general review from Macworld, which helps explain why the 8 core chip is probably the best bet for most users. If you want to dive deeper into the different CPU configuration options and what they mean, check out this post from iOS Dev Marco Arment. Understanding the Turbo feature on these new chips is really important. There have been some reviews critical of the new machine, Dave Girard at Arstechnica has some interesting points.
Finally, for those of you interested in future upgrade/exapandibility of the Mac Pro. Check out this great teardown from iFixIt.