...she hasn't had any major public gaffes that I'm aware of.
This is actually completely untrue, but the fact that you don't realize that is why it's ok: we've seen it already and no one cares. You can only be outraged about so many insubstantial things for so long, and bringing things up now would seem like beating a dead horse. You can hardly bring up shit from when she was first lady now, and I'm sure not many people could cite exactly what it was that she did with her time then.
But anyway, Clinton's campaign is a reminder that national politics is strongly influenced by "Clap your hands if you believe" magic: Clinton's air of invulnerability has become actual invulnerability (surely it's not because of her massive logistical support network that has been quietly building up for 8 years now). She's invincible because people think she is invincible.
Incidentally, could someone explain why we keep calling the Clintons a dynasty? Dynasty implies multiple generations, and I don't seem to recall there being more then one Clinton as president. Chelsea doesn't seem much interested in it either. Which reminds me: I think we can all agree, in any case, that the real point of electing Hillary is to elect Bill Clinton as First Lady.
That's even IF Jeb Bush gets the nomination.
This is a much, much more relevant question. Unlike 2012, where the republican primaries effectively functioned as an extended roasting of their inevitable candidate (It was basically "Anyone but Mitt" for several months there), there is actual opposition here. For one, Jeb Bush's protégé: Marco Rubio, who will also be announcing Sunday (Their base of support overlaps tremendously). Rand Paul is likely to be a much more legitimate threat than his dad as well, with a broader base of support and significant advantages in the early primaries. And Scott Walker seems to be gaining momentum as the premier choice of the social conservatives (though Ted Cruz may be drawing some of that energy). And those are just the top prospects; outside of that territory we have everyone from Bobby Jindal to Lindsey Graham, from Rick Perry to Carly Fiorina. The Republican primary is gearing up to be extremely competitive, but I'm confident it will succeed in producing the compromised, "That's not quite what I meant" candidate I expect.