has any one used both sram x0 and x7 shifters and derailleurs? whats the difference. l have X-7s and l was wondering if the is any noticeable difference between the two. (I am talking performance, whats the difference)

Your being too specific; nobody here knows.
However you should go with what ever you think is best.

l ride with x7's, but hav not tried x0 is myself, but the difference in cost is quite high due to the materials in the x0, l think they are a hell of a lot smoother and a lot lighter, but unless u'r a freakin good rider it prob not worth it because of the price.

X7 is meant as a cost effective, quality system. It is a great system for the average rider who does not have large amounts of free money to throw at a bike.
X0 is what l like to call professional grade. These r the more expensive parts, lighter, & possibly more durable.
l think of these comparisons:
X0 to Shimano XTR
X9 to XT
X7 to LX
The XO does shift a little faster due to the carbon fiber being stiffer. It is an immediate reaction time, whereas the X7 has a modest delay. The XO seems almost telepathic whereas the X7 is a modest amount more deliberate

BTW, I've been using the X9.0si with twist shifters for the last 8 years without a single hitch. These new X9 is even better. l have never been disappointed & would highly recommend them to anyone.