i've seen the Mona Lisa first hand....only thing special about it is the huge crowds taking pictures of it. They've put a darkened glass box around it to protect the picture from flash photography.
I cant recall the names of other art in the louvre...there are some nice stuff there.
i prefer the artwork in uffizi in florence, italy anyway...spent half hr looking at birth of venus by boticelli (spent 30 secs on mona lisa).