It's the ancestral homeland of the Humans, as it's the seat of Arathor. It has substantial significance for the Human and Forsaken factions, as it is essentially their heritage; Forsaken are formerly from Lordereon and Humans, the playable ones, are from Azeroth (New Stormwind). Ever since it was mentioned that Varian would have to go through the High King trials, it was speculated that retaking Stromgarde could have been one of his trials, perhaps proving that he is worthy in the eyes of his own race before going on to prove himself in the eyes of his Allies.
Probably about as much as any diehard forsaken fan gushes at the mere mention of Sylvanus.