Things you don't mention: How do you like to ride? Fast all the time? Slow and steady? some of each? Do you like a more aggressive position or do you prefer a more relaxed?

Do you ride using the hoods and drops or do you ride on the flat part of the bar 99% of the time (like many folks riding with drop bars because that's the bike they are stuck with do)?

How much load do you carry on a regular basis? Is any weight savings on the bike itself going to be insignificant compared to your book/laptop/stuff load? (trying to save even 3-5 lbs on the bike if you still carry 25 lbs or more in accessories and load on your rack seems pretty silly.)

You mention that it is all paved roads -- what size tires do you like to run? if you're used to running 27 x 1 1/4, you might find it punishing to run 23 or 25c tires. Urban streets tend to be pretty rough, so I'm a fan of having some robust tires, which most modern road bikes won't fit. Cyclocross bikes do, though. How about weather -- will you ride 4 seasons (do you have 4 seasons)? Snow? rain?

New can be good (I bought my latest commuter new), and so can used (my other two bikes are used). One advantage of used is that you can save enough (hopefully) to change out things you don't love. OTOH, if your budget covers the cost of a bike that's 'perfect' out of the box, then great. Also, do you do your own maintenance/repairs? depending on your LBS, you might well get the cost of tune-ups/adjustments covered for a year, or even 'life'. One thing to consider, also, is whether there are any end-of-year specials/clearance sales which might make new look even better.