"Flaw" is subjective. It's an inherently conservative -- in the traditional sense, not the "$700 billion bailout" sense -- tool to prevent a slim majority from doing something controversial.
Where it breaks down is when the opposition party is a bunch of fucking pussies and one party controls all three branches of the government. This, of course, is exactly what happened between 2003 and 2006.
I recall thinking, back in '05 when the Republicans sought the so-called "nuclear option" of declaring filibusters unconstitutional, "Wow, you know, that's going to suck for the next couple of years, but in the long run they'd really be fucking themselves, because the filibuster is an inherently conservative weapon."
Sure enough, if the Republicans weren't filibustering pretty much EVERYTHING that hit the floor, we'd likely be better off right now. Of course, that doesn't solve the veto problem, but of course veto power cuts both ways and we'd be happy to have it if we had a Republican Congress and Democratic President.
Assuming, of course, it were a Democratic President who actually EXERCISED his veto power. Yeah, I'm still pissed at Clinton for signing the DMCA.