Since upgrading to 0.7, we've had a significant issue with the colorbox, related to load times.
If the customer clicks the "add to cart" button on one of our product pages before the web page completely finishes loading, the colorbox does not display. Instead, the cart displays on its own page. This might not be a big deal except (1) it's really ugly -- essentially a loss of formatting -- and (2) there's no "continue shopping" link from there back to our site. The product as added to the cart also displays the famous X and Y codes, which gives us some indication how often this is happening.
*Footnote on load times: we had to locally cache the foxycart CSS, images, and JS files to keep reasonable load times-- we were seeing load times as high as 25 seconds yesterday due to linking to the foxycart files on your CDN. Previous times that we've looked at our load times, those foxycart files have loaded darned fast, so it seems that your CDN is only fair-weather fast.