BJH and Festival, I think you have both summed up Armstrong perfectly.
I can't stand him. I've always been suspicious of his doping record (or lack thereof). The doping is almost a separate issue though. His generation of riders doped almost to a man. But it's not just about the drugs. We've forgiven Millar (who I'm told is not always the friendliest chap), Ullrich was an incredible talent, we all loved Pantani, I'm indifferent to Riis, Museeuw was and always will be one of my favourites. We know cycling is riddled with drugs and has been through the ages, most of our heroes are tainted but I just see it as part of the reality of cycling (an unpleasant reality, but reality nevertheless).
Sure Armstrong's story is inspirational - no question, but like BJH says,the people inspired by him can only succeed through their own efforts.
Ultimately, for me, it comes down to him being thoroughly dislikable - I don't like his meally mouthed answers about testing or the threats of lawyers, his telling Festival to 'f--- off', the way he treated riders he didn't like with total disrespect, the general disrespect he showed the sport for so much of his career.
Merckx said to him when awarding him the 6th or 7th tour 'Congratulations, now you are a great of the Tour, but not a great of cycling'. I'm twisting his words but to my mind that last clause sums up Armstrong for me.
Hinault, Merckx and Anquetil all dominated and won races almost at will (or solely through sheer will). Sure, they also had the best teams money could buy and they made plenty of enemies but I always got the impression they were well respected and they were known (most notably Hinault) to stand up for the rights of the riders, not just himself (though I admit he was most passionate when it was his interest at heart and the 86 saga was a particular low). Regardless, their retirements were all genuinely mourned.
The comeback was yet another unneeded chapter.