It's the one I use the most, but in my experience it's lagging behind the Twitter accounts. It's also noisy because it puts last-minute outages at the same level as minor month-long schedule change (which can't be dismissed), so some lines (eg. line R) are almost always displayed as having issues.

This app is just garbage. Can't even use it if you are rooted.

For me a website is much more accessible than a phone app in many situations.