As a web app developer and frequent user of the MBTA site, I was appalled when they rolled out the new site. While it may be totally broken in Opera, it was functionally questionable in IE and FF as well. It's great to update a site, but they made many UI mistakes such as relocating pertinent information under cryptic menus. I'd used the site for the past 18 months and happened to have an urgent need for finding the schedule that day (overslept), and was furious that it was so difficult to find.
No amount of careful planning will ever replace dumb luck.