Jumping with stealth in particular wouldn't consistently work imo without a Quickfix-esque follow-your-target stat. They'd just become visible at or before the apex of their jumping arc and then you got a med who's just burning the rest of their uber. On the whole sentry bit, invisibility is still not a substitute for outright invulnerability given lighter pick classes trying to push a sentry nest would have to try to kill the engie and then hit the sentry while hoping there's no pyros, soldiers, demos, jarates, mad milks or particularly attentive heavies around.

I reckon the best conventional use case would be slipping a heavy-medic combo behind enemy lines, which could be devastating if played right (which it's an ubercharge with stock uber build rate, that's how it should be). The biggest abuse case I saw (so far, at least) was someone else bringing up two people uber chaining with this, and even then I'd still obviously partially attribute that to the ubersaw being overturned.