There are two aspects of the Champion's dailies worth nothing:

1) If you need major city rep with a city other than your "home" faction, the Writs are not unique and can be saved up until you unlock the ability to champion a city you do need rep with.

2) Pay attention to the cost of Runecloth on your server. If you can get 3.5 stacks for 10g, you're better off getting the money bag and buying Runecloth for your rep, at least financially. Runecloth costs seem to be dropping a bit with the addition of the Argent Tournament, so this may actually be a reasonable route.

The Champion's dailies are a fun diversion for now, but I can't say as I'm looking forward to killing the same elite and the same mobs down by Icecrown Citadel every day for the next 8 months to get all the mounts, pets, tabards, etc. Hopefully the addition of the Coliseum in 3.2 will bring additional means of earning Champion's Seals. In the meantime, I wish people on my server would stop tagging the Commanders and kiting them away and keeping them alive.

Presumably yes. You could just destroy the Valiant's Seals from your inventory if attempting to complete the quest gave you an error. If you did that, you could theoretically be earning 1k rep per day with two factions--1k from the Writs from Champion's dailies, and 1k from the Valiant's dailies. You wouldn't be able to earn 2k/day from the same faction though, as you wouldn't be able to buy their Commendations until you complete the Valiant training and become a Champion with them. (Though I guess you could save up the Writs until you're halfway there, then upgrade to Champion and turn them all in.)

You can also do the quest to start all over, with another city, without losing the quartermaster from your own city. You just have to start over, with that city, and in 5 or 6 days of doing dailies, you can then try to become a champion of that city as well. within 4 weeks, you should be able to have all 5 cities to be a representative of.

If this was already mentioned, I missed it.

You can go beyond 25 valiant seals. I had one of the weapon retrieval dailies from a previous day that I missed out on doing the dailies. After doing the previous day's weapon retrieval, I got the current day's quest too. I still have the 2 extra seals while I'm doing the valiant quests for Exodar rep now and they even count toward the new valiant quest total.

If you are looking for off city faction, run the level 1-10 starter quests for that race. Faction return is always 100% and 10% of that is applied to all the other cities.

For the ones who like to run BG's, you can get exalted with Alterac Valley, by turning in Storm Cyrstals. Once you are exalted with the Stormpike, you then get alliance rep for each set of Storm crystals you loot from killing the opposing faction. (You will need alot of them, but then again, some people are running alot of BG's). No sense missing out on free reputation, especially if it's for Alliance rep, it goes for all 5 cities.

(This will also work for the horde side, but I'm speaking from the Alliance side of course)

Lets get back to exciting Argent Tournament discussion!

To be honest, I'm not really sure it needs to be that much faster... it's a weird sort of state where there both isn't all that much to buy, and a whole lot. If you want to get every last tabard/mount/pet, sure, that'll take way too long. But realistically, you can get the mount, pet, and tabard of your faction in five weeks or so or champion dailies; a lot of dailying, but that's for something in each "slot". The mechanical rewards are outright worthless if you're actually raiding, and even if you aren't, you can get all of the applicable ones in less time than that, even with the possibility of multiple specs.

Of course, this is a big assumption to make; I know there's definitely people who really want as many of the pets and mounts as possible, and if they're adding new ways to get the seals in the future, they may well add new rewards to make it worth the effort. And that brings up a seperate issue; unless there's a burning need for one of the equipment rewards (a freshly 80'd alt needing a purple weapon or whatnot), there's no reason not to just save the seals until 3.2 appears on the PTR. It's not like flavor items ever go "bad", and if by some chance they remove a particular item from the vendor, there will doubtlessly be ample PTR warning and you'll be in a perfect position to pick it up. Hedging your bets, if you will.

I've noticed an interesting anomaly in the Champion's arena area of the Argent Tournament. All the races present are championed by 1 male and 1 female representative... except for the Night Elves. Is this a matter of Blizzard adhering to the lore, where hunters and sentinels are generally women amongst the Night Elves, or is this for a more prurient reason?

While it's nice that we finally have another way to grind major city rep, I can't really understand the point of adding this event. Why did Blizzard add this?

I think you answered your own question there. Runecloth was going to become more and more annoying as time went on, and this is a far cleaner way of allowing people access to the city reps. The Argent Tournament really isn't going to be obsoleted as time goes on, like a Raid would, so its a good investment for them design-wise, as people are probably still going to be doing it a year from now.