Starting with the Mac Pro question, the most common complaint over at Engadget is obviously that of price. The Mac Pro isn't "cheap", but the obvious problem with the word "cheap" is that it's all relative. If you think the price/value ratio is okay, then the Mac Pro certainly isn't expensive. In any case, I'm not going there - I don't need a Mac Pro.
Still, some other complaints appear to be pretty valid. A lot of people are asking for Blu-Ray, which I think is a valid thing to ask of such a high-end machine. You could vaguely argue that it doesn't make any sense yet for average desktop machines or laptops, but when it comes to these high-end workstations used by professionals, I don't think there is a valid excuse for not offering Blu-Ray at least an an option.
Another pain in the bum, according to many Engadget readers, is the RAM limit on the single processor machine. Currently, it can't take more than 8GB of RAM, while competitors offer no such limit at all on similar machines. 8GB sounds like a lot to me, but professionals often need more than that.
There are also a lot of complaints on the video side of things. The default cards are too slow for such machines, many claim, and there are far too few options to upgrade to, and even those are outdated. In addition, anyone who has ever had to shop for a Mac video card knows the ridiculous price difference between Mac and "normal" PC video cards.
Then there's Mac OS X itself, which we add into the discussion to make it more interesting for OSNews. What would you change? Personally, I'd love to have a better file manager built-in, one that does not suffer from split personality disorder like the Finder currently does. I'd also like a decent way to update applications across the board, a ban on packages with installers, and App Zapper built-in.
Fire away, people.