Is 50cm really the right size for a 5-3 woman? Sounds big to me, although road bikes aren't my thing. I'd look at ebay, using the completed item option, and check a wide range of roadbikes and hybrids - there really isn't a strong performance difference between the two genres if you make sure the hybrid has a rigid fork. I'd also question the use of a racing bike as a first commuter; narrow chain stays may prevent you using fatter relatively pot hole proof tyres, the riding position will be less friendly, and hybrids tend to have better braking ability. Oh, and they can usually take racks and mudguards, which real racers can't. Lots of people ride their first triath on an MTB with slicks and aeros - its only about 5mins in an hour slower than a dedicated triath bike.

An outstanding bike to buy can be a cyclocross bike - these are basically tougher racers with room for wider tyres and more powerful brakes. Great commuters. I've heard that the Motobecane Fantom CX is a great deal on sale right now (I have no idea why this post has gone into bold and won't stop) - a new one is less than that used C'dale. Ask on the Cross forum. But it may or may not be able to take mudguards etc; work out how important this is to you.

Take a look at

http://www.bikesdirect.com/products/...m_cross_cx.htm

I think these are actually re-badged Fuji's, which means the engineering should be excellent. 99% as faster as a racer, 99% as tough and fast braking as an MTB, and an amazingly good price right now. If I was in the US I'd buy one just as spare bike.