Our Elantra developed a knock at 130,000. Hyundai covered 75% of the replacement which left us paying $2000. In a way I'm kinda glad ours ended up knocking because it's not everyday you get a brand new motor installed for $2000. The rest of the car is still doing great so I probably would have taken that offer even if it wasn't knocking.
From what I understand the majority of the knocking issues were due to a manufacturing error causing piston slap and that has been resolved.
All said I wouldn't have a problem with buying another Hyundai.