This is the first of two posts that attempt to answer questions that I get asked a lot.
"How do I pick out a road bike?"
1 - Brand
All of the major brands are good. I don't recommend buying a catalog brand because it's clear to everyone that you sold out your local bike store.
2 - Frame material
This is a complicated subject with many strong opinions. I'll throw out mine and you can see what sticks. For weight, lighter is better period. Stiffness is one of those give and take categories. In general, squishier materials give a better ride with a loss of power transfer. Squishy frames flex when you're cranking hard and that flexing takes power away from the wheels.
Weight (roughly lightest to heaviest)
Aluminum and Titanium
Stiffness (rigid -> squishy)
*The Trek Madone bikes seem to be an anomaly here - super light, comfortable, and stiff. My racer friend loved hers more than any other bike she's had (before she drove into the garage with it on the roof rack).
3 - Components
Components are things like shifters, derailleurs, brakes, crank, wheels, etc. There are a lot of very nice frames that have absolutely crappy components in bike stores that I don't understand right now. The components have a big impact on day-to-day function. Cheap derailleurs and shifters don't work for crap. There are three major brands - Shimano, Campognolo (campy), and SRAM. Shimano is by far the most prevalent of the three. The biggest difference between the three is how the shift levers work. The best thing to do here is to ride bikes with all of them and see what is most intuitive/comfortable for you.
Shimano Road Components (best on top)
Anything else isn't worth it.
Campognolo Road Components
4 - Set A Price
For new bikes you have to spend at least $1000 to get something that will last for a long time if you end up being an enthusiast. Spend much less and you'll end up replacing your $300 bike with a $1200 model in one year (yeah I'm talking to you DJ).For a shimano bike with a mid-level frame, for $1000 you'll get a mix of 105 and Tiagra. $1100 gets a full 105 bike. $1200-1300 gets a full ultegra bike.
With the exception of carbon fiber frames, used bikes are almost always a good deal. Carbon fiber frames are difficult to buy used because crashing can cause invisible damage, and when a carbon frame fails, it epic FAILS!
5 - Clothing/Misc
Bike clothing may be unattractive, but it's functional. Dress to be just a bit hot standing still in cold weather. Get a good helmet deal at REI Outlet.
If you're serious, roof racks are the only way to go. It makes transporting bikes sooooo much nicer.