As an out-of-towner I have to give props the Monononononongahela for being a viable form of public transportation in a city that seems to be struggling a bit in that sense, but as for being something super amazing for tourists to see, I wasn't terribly impressed.
At $3.50 for a round-trip ticket, it'll by no means break your budget, but I don't know that it was necessarily worth the headache of trying to buy a ticket at the top with one attendant on duty and what appeared to be a line full of people who had never seen a touch screen device before.
The view was pretty cool but the realization that the incline isn't a ride and is a form of public transit is sobering.