Considering how many people here started disliking Bush and calling him a squishy RINO, thanks, you are helping with the case against Rand.
Well, just speaking for myself, my biggest disappointment with the entirety of the Bush presidency can be summed up in one word: Spending.
Domestic Spending was grossly unrestrained. And even if one argues that Military Spending has to go up in time of war (or major "use of force" actions), there's expenditures that could be cut to offset some of that (I tend to think that perhaps we've provided Europe with too large a "defense subsidy" for too long, but that's just one idea).
Since Spending Bills necessarily come to the President's desk from the Congress, my biggest hope for Rand Paul is simply that he'll be one of the Senate's strongest voices for reduced Spending.
Heck, I'm a huge Tom Coburn fan, for exactly the same reason; and I don't agree with him on everything, either.