Roadie help, 2004 Giant OCR2 for $550?

I am going to purchase my first road bike, and i figured i might as well start used. Anyways, i will be doing a triathlon with it in September, and other than that doing a decent amount of riding on it. As far as the Giant OCR2, i looked at it today at the LBS and it seems decent for a first. I found one on my local CL for about $200 less than new. Just asking for some advice, i know it comes with Shimano "Sora"(sp?) vs. Shimano 105(which i heard is better). Any advice is welcome.
Giant OCR2