These are great bibs for the price. My favorite bibs are the Free bibs from Castelli; but at half the price, the Velocissimos are hard to beat! I tried on the white version at the LBS and echo that they don't leave much to the imagination. I came home and bought the anthracite version online.
With regard to the fit of Castelli gear: yes, I've found their jerseys and bibs have a more slim cut when compared to a number of other companies. If it's your gig than you can't go wrong with Castelli kit, if not maybe look elsewhere.
One negative on all Castelli kit I've owned: their stuff doesn't stand up too well to the abuse of my top loading clothes washer. I wash them using the gentle cycle or wash my kit by hand. It's worth the effort, to me, because I really like the fit of their gear more than that of any other brand I've tried (PI, Sugoi, Fox, Descente).