ER is at its core a social simulation game, possessing ingredients of titles like The Sims with traditional role-playing elements thrown in for good measure... In addition to fulfilling these game objectives, players must also keep tabs on relationships with their patients and fellow physicians, energize and nourish themselves by eating regularly (or at least grabbing a can of soda for a quick jolt of caffeine), washing up to maintain their hygiene and getting into the gym now and then to keep fit.
...In addition to the perks, ER also allows players to make use of special abilities, which are status boosts that can be stacked three at a time to improve performance. One might choose to use a Photographic Memory ability, which would allow them to gain a certain amount of experience points just from observing and being in the presence of other doctors as they handle their patients. The special abilities are swappable, so players can freely switch between whichever abilities are available to them and best suited to complete their current tasks.
Based on the review, the game seems more about character development than it is about medical simulations and correct diagnoses (which is featured heavily on Step III). So, from my perspective, it's hardly test prep, and the ER setting may be too familiar to enjoy spending free time in. But, in terms of escapist wish-fulfillment, it could be fun to play an all-knowing attending when mired in the depths of intership.