[shiroiuma]

I've generally found they're all correct. Sometimes, I run into situations where a particular exit is closed because it's after-hours (some stations close certain exits when it's late), and Google Maps doesn't realize this, but I haven't noticed any exits being outright wrong.

I think this is probably a local issue: Google Maps is better in some places than others. Google has a huge office in Tokyo, in Shibuya overlooking Shibuya Crossing, so Tokyo is probably one of the best-supported cities in GMaps for this reason. Other cities might not have such accurate information.