Krum makes his first appearance in Book 4 as the Seeker for Bulgaria - a world class Quidditch player. He hunches, has an odd nose, and speaks english badly. Apart from that, he's a pretty nice guy.
And... he has a crush on Hermione. Ahem. He's also the champion of Durmstrang school in the Triwizard Tournament and competes against Harry. Apart from that, he isn't really that important. ron both likes and dislikes him - he first buys a miniature Krum figurine and then proceeds to tear it to pieces. He first screams at Hermione for 'fraternising with the enemy' when she accompanies Krum to the Yule Ball and then proceeds to ask Krum for his autograph. Odd.
And Harry and Cedric - before he dies, that is - both think he's 'okay', which I suppose means that they don't think he's evil. He isn't, either (though if you read Harry Potter polls you might think otherwise). (^.^)