It also comes at a time in the expansion where most people have probably earned exalted status with all the factions in WotLK and are probably wondering what was left for them to do. The Argent Tournament gives them some focus back. And as far as the "grind" goes, it's a relatively short grind, taking just less than a month to Champion all races, if you do the dailies every day. And they remain a good source of gold after that.
Day 1-2: Aspirant dailies.One caveat however. Do not spend your Valient's Seals on those pets, mounts, and weapons until after you have Championed all the cities, because each one requires 25 seals (5 days work) to get to that race's Champion quests.
Day 3: Aspirant dailies and Valiant dailies (#1). Valiant home city.
Day 4-6: Valiant dailies (#1).
Day 7: Valiant dailies (#1) and Champion dailies. Champion home city, Valiant second.
Day 8-12: Valiant dailies (#2) and Champion dailies. Champion second city, Valiant third.
Day 13-17: Valiant dailies (#3) and Champion dailies. Champion third city, Valiant fourth.
Day 18-22: Valiant dailies (#4) and Champion dailies. Champion fourth city, Valiant fifth.
Day 23-27: Valiant dailies (#5) and Champion dailies. Champion fifth city.
Day 28+: Champion dailies.