The basics of this plot have been used many times before – an individual wakes up from a coma to discover that what he considered to be "reality" has changed in some fundamental, unsettling and "wrong" way. Done well, it's always a winning theme. In this case, Commander Riker wakes up 17 years in the future to discover that he is now Captain – and in charge of completing peace negotiations with the Federation's former foes, the Romulans.
The show had done a nice job of setting up the Romulans as the key villains on TNG during the 3rd season (they were more interesting than the Borg, in my opinion), which provides the perfect launching pad for a story like this. Given the way the episode is set up, it's pretty clear to most viewers from the outset that Riker is caught in some sort of cunning, devious Romulan plot. Riker, despite initial suspicions, begins to acclimatize himself to the new reality – just before himself catching onto the Romulans' machinations.
But that's not the final wrinkle in this tale, which I won't spoil. Let's just say that while the twist at the end isn't bad, and that some sort of twist was absolutely necessary, I can't help thinking that the writers could have come up with something even better. Nevertheless, one of the better episodes from the 4th season.