Had my Defy 1 for going on 3 years now, and have put in roughly 8,000 miles... It is one of the lightest bikes in its class, and I have loved riding it. I have only a few minor quibbles:
1. The geometry puts me in a little too relaxed position - most of the guys I ride with are in a more aggressive race-style position (flat back nearer parallel to the ground, which is how I used to ride in my youth)... I haven't been bold enough to start radically altering my Defy by dropping the stem down lower- I'm not even sure I could obtain a race-style position with the relatively shorter top tube... As it is, I have pushed the saddle back pretty far, and rolled the handlebars down a notch.
2. The saddle, while looking good, wore out after a year.
3. Cheap tires.
Otherwise, it has served me well thus far, and while not the sexiest or most expensive bike on the road, it offers a great ride and features for its price.