The release schedule argument basically runs as follows. One side asserts that you should allow all parties to access all content at once, otherwise it is unfair to people who can't access the harder difficulties for whatever reason, since they pay a sub just like everyone else. What's more, it encourages elitism to open the easier content later.
The counter-argument is, essentially, and there is a risk of reductionism on both sides of the fence here, that it shouldn't be the case that the harder difficulties are the last ones to kill bosses, that the epicness of a World First Garrosh kill would be detracted from by having done it three times in LFR already. What's more, there's a big risk of raider burnout from people feeling like they have to run all the bosses every week in LFR, and staggering that release helps with that issue. Hardcore raiders will be required to do this by their guilds, and it's likely that Flex will be added to that to-do list. Even casual raiders would likely feel oppressed by this requirement.
Additionally, for players who just want to see the fights and don't much care for progression, their raid content would be done on day one, if everything was opened at once. Lastly, in this summary, it is undeniably the case that, apart from the handful of guilds racing for realm first, or world first, players progress through fights at a slow, steady pace. Based on my own casual raid guild, LFR sees the end bosses far, far, far before casual normal mode raiders. It should not be the case that you can see everything on day one.
Now the question is, which side of the fence do you fall down on? Do you think that everything should be open to everyone on day one? Or do you think the staggered release schedule works better. As Bashiok elucidates, Blizzard definitely falls into the latter camp. And I do, too.
The main reason for that, in my opinion, is a mixture of two of Bashiok's many points (somewhat abridged):
While I think his other arguments have merit, these are the clinchers for me. I've mentioned before that I am not a hardcore raider, but while there are several wings of LFR open, there is this feeling that, like most of the rest of my guild, I should be doing LFR. If I'm not doing LFR I'm letting the side down, I'm a hindrance, I'm holding my friends back and being selfish. And I don't like doing LFR. It's not fun, it's dull, and the only thing you get out of it 90% of the time is rage. Loot, yes, but mostly rage.
If I could go back in time to just before Dragon Soul, I would take footage of LFR now, show it to Blizzard, and try to persuade them never to add it to the game. Flex is a far better solution, it requires pre-made groups, yes, but addons such as oQueue or sites such as OpenRaid make this easy to achieve on either a pre-set schedule or spur of the moment.
I also don't think that it should be the case that the easiest difficulty is the best way to see the end-game boss at high speed. Yes, LFR will see it before I will on normal. Possibly even with Flex, it depends on how the difficulty works out for my guild, but nonetheless, I love to follow the world first race, to see progression guilds post videos as they hit bosses, and to have the suspense of finding out just what happens at the end. And I don't think all that should be taken away for the benefit of those who want to do LFR on day one.
Now, of course, part of the discussion here has to be about Flex raiding. Bashiok asserts that the release schedule of this raid, if you remove Flex from the equation, is exactly the same at the Throne of Thunder one. And he's right, even down to the 2-week gap after wings 2 and 3. So what is Flex changing here? In a way, it's changing nothing at all. The release schedule is identical. But it's another difficulty which is getting to see things before LFR, and it's not hard to see why that has people riled up, and why I'm sure I will get my fair share of anger for stating my opinions above.
Blizzard is clearly trying to push LFR raiders into the new difficulty, with the offers of heirlooms and the faster unlock schedule all there to help, and as you have gathered, my personal stance supports that. But it's not hard to see why people resent it. LFR is really easy to get into, you simply click a button, and you're in a queue, of a varying length. When your queue pops, you head into the raid, kill some bosses, and leave. You're done.
But it was never so hard to PuG raids before LFR. Just think back to Firelands, not so long ago, when trash runs were going on almost constantly so that people could farm the reputation that it rewarded. You hopped into trade, you picked up a group, you went and killed trash. And yes, you wiped every now and then! But it was fun. And Flex will allow you to do exactly the same, only cross-realm. My only concerns for Flex right now are that it will focus on 10-man sizes in PuGs, thanks to the lower co-ordination required, and the ease of getting hold of people. I also worry that people won't quite know how to make up larger groups, composition-wise, with healer numbers particularly, but none of these are big issues.
There will be PuGs for LFR-focused players to get into. People will want to do this content. You will be able to get a spot. Don't you remember Tol Barad's bosses? It'll be like that, only all your battle.net friends can come too. And, to preserve the feeling of raiding being something that is tricky and requires some co-ordination at least, I think a small barrier to entry is a good thing.