The idea of telling an epic story from the point of view of the little people involved is respectable, and can produce marvelous results. The primary problem with The Hidden Fortress, however, is that Kurosawa takes two characters who are usually minor stereotypes in stories like this, and expands their roles dramatically while leaving the characters as stereotypes. In this case, the two peasants are greedy, selfish cowards, concerned only with making a quick buck and saving their own skin. Kurosawa may have some insulation against charges of classism by having another lower-class character introduced later in the film, but while she is more noble, she's still primarily a trait (loyalty) over a well-developed character.
The story of a young princess suddenly thrust into full responsibility for her entire family and nation, while a loyal - but defeated - general (played by Kurosawa favorite Toshiro Mifune) attempts to deal with her stubbornness and grief is a strong core, and many of the film's best scenes focus on that. It's just something of a pity that the story is watered down by the often-grating antics of the two-dimensional peasants.
A modern description of The Hidden Fortress is somewhat incomplete without mentioning its influence on George Lucas and Star Wars. Lucas is a huge Kurosawa fan, and the Criterion edition of the film includes an interview with him on Kurosawa's influence. The Hidden Fortress is most often cited as the direct inspiration for the characters of R2D2 and C3PO in the roles of the two peasants (although the robots are much less obscene and violent). The opening of The Hidden Fortress begins with the two fighting, separating, then becoming captured and enslaved before an unlikely reunion, much like the beginning of A New Hope.
It's also easy to see Kurosawa's influence on Star Wars in perhaps the best scene of the film, a duel between Toshiro Mifune and an enemy samurai.
The slow buildup of dramatic tension, followed by moments of dramatic action combined with the use of terrain and props bring to mind the best lightsaber duels from Star Wars, most notably the finale of The Phantom Menace, arguably the best section of all three prequel movies.
Although I've been fairly critical of it, The Hidden Fortress is still a fairly likable film, but it pales in comparison to some of Kurosawa's other masterpieces. Star Wars fans and Kurosawa fans should find it extremely interesting, but a Kurosawa newbie may be better off with The Seven Samurai or Rashomon.