Went there twice almost a month ago.
Devoured cold appetizers (housed in the display case under the counter) of bean curd skin, spicy cucumbers, seitan and mushrooms, and spicy beef tendon. All of their small cold dishes are really tasty. Pork and pickled cabbage (really pickled mustard, but everyone calls it cabbage) soup is suitably sour, although I wish they used more tripe. Don't know the name of these dishes: slivers of beef with lots of sliced green peppers (pleasantly hot) is tasty, and Sichuan eggplant is both mildly sweet and satisfyingly spicy.
It's hard to find proper Sichuan ma po dou fu; for many years, Four Rivers has been the only place that I've found in the greater Philadelphia area that serves it. However, sometimes FR makes it slightly differently--I suspect different chefs. The ma po is served in a flat oval dish rather than a deep round bowl, without as much delicious deep red oil, and rather vinegary in taste when compared to the transcendent version. The beancurd isn't as soft. All the components are there, but the spices are just a bit unbalanced. Still very good, just not the truly amazing dish I was craving.
But most of the time, their ma po dou fu (listed as "Ma Boa") is soft creamy cubes of tofu in a spicy, vibrantly red, oily sauce, accented by Sichuan peppercorns. (Their supply apparently didn't diminish during the recent ban, and I was content to be ignorant of the reason.) Love this dish.