i have the x4 keyboard and like it, but mostly for gaming. The one advantage I really like is that there isnt a limit on how many keys you can press.
A quick test would be to type this while holding both shift keys:
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
Some keyboards will not be able to type all the letter due to this:
Rollover (key) - Wikipedia, the free encyclopedia
As for the mouse I dont think it matters as much, but that's subjective. Personally I just love a mouse that feels right in my hand more than anything.