Tokyo Metro, Toei, Keikyu, and others have rolled it out across a significant chunk of their lines at this point.

You can get to a significant portion of the network... So long as you don't have to take a JR train.

My only complaints about Contactless Cards from Visa/Mastercard/etc. Is that they're significantly slower than FeliCa. I can sprint through a gate with my Pasmo; I have to stop with my Visa.

For Visa, the closest transaction processing happens in Colorado. So they're slooooooow.

Disclaimer: Fmr Visa, current PayPay employee. I hate payments.