ORIGINAL: anarchyintheuk
For a master Lee was caught with his pants down pretty often: Antietam (no fault of his own this his orders were intercepted but he could only have been saved by McClellan's 0 aggression rating), Fredericksburg (helped by the US War Dept.), Chancellorsville (saved by Hooker), Gettysburg (blundering into a major engagement unprepared) and Petersburg (saved by our friend Beauregard and the fact that the AoP II Corp had been butchered in the Wilderness).
As far as Stuart leaving Lee 'blind' before Gettysburg: 1) Stuart took 3 brigades of cavalry, the ANV still had 4 remaining, 2) it was Lee's own command structure that left his remaining cavalry inactive because no provision was made for a 2nd commander to take over while Stuart was wandering around, and 3) after Brandy Station, Lee should have made sure that Stuart performed his proper screening and reconnaissance role and not trying to restore his reputation.
Just my $.02.
Chancelorsville was Lees greatest victory and the epitome of what I mean by taking a hell of a risk by dividing his forces in front of a superior foe. You say he was helped by Hooker, but no more than he was helped by Grant at Cold Harbour. I think one of Lee's greatest traits as a commanding officer was his ability to read and understand his opponent so well. So for Lee, there was no question of how Hooker would react at Chancelorsville regardless of whether or not Hooker was knocked silly by the shock from an artillery shell, the battle would have played out similarly. In fact, I'd almost argue that it would have been better for Lee had Hooker had his full senses.
Antietam, as you say was no fault of Lees and considering the forces that opposed him--helped by McLelan's timidity--I'd almost argue that the withdrawal of the Army of Northern Virginia from Maryland means that Sharpsburg was really a great Confederate victory.
Finally there is Gettysburg, and this is what I meant by the "price" of Lee's aggressiveness. Despite the intial contact with the Army of the Potmac really being the fault of Stuart, Lee did not (unlike Antietam) have to give Federal forces a General battle. He chose to fight on that field when he could have still easily manuevered and dictated the time and place of a general engagement.
Unfortunately for the Confederacy, Lee got in his mind the he would fight it out then and there and refused any council, which was offered, not to do so.
Though I will say, despite being (again) helped a bit by Meade, Lee's withdrawal back to Northern Virginia was a work of his genius, though the genius of an army on the losing side of a war, after a lost battle, is not something often noticed.