I've had a Murcielago for 6 months now, and put 5500 miles on it. No problems whatsoever. Along with that, I've driven it hard.
I also own a Merc SLR, performance-wise about the same, but the Murcielago is essentially $100,000 cheaper... and in my opinion, better looking.
http://my.break.com/media/view.aspx?ContentID=193638