Virtual citi cards are nice in theory, but the web app to make them it pretty cumbersome to use, and the desktop app to do it just feels super icky. They also have short expiration limits, so it's not great to use for subscriptions where you ideally set and forget.

Edit: the web app for Citi was also a flash app last time I checked (few months ago). That plus them not supporting 2FA for every login makes me not use it.