I think tiers of play are a great idea, but they are largely useless without the proper adventure support.
What made the BECMI model work so well was that the adventures produced for each boxed set were markedly different. You went from dungeon crawling to wilderness exploration to kingdom building to plane-hopping to godhood.
I think one problem that 3rd and 4th edition both faced was that the adventures were designed more or less in the same manner. You basically went to a site and fought monsters, whether they be orcs or Orcus. If you're going to have tiers of play, I think it's best to make the adventures significantly different in feel for each tier. Otherwise, it just feels like you could just add bigger monsters into the same adventure and get more or less the same result.
I've always loved the overall structure of BECMI D&D. AD&D implied a similar progression from dungeon crawling to wilderness adventures to building strongholds and establishing a territory. BECMI just made that framework more explicit and expanded it to encompass the quest for immortality (the focus of Set 4: Master Rules). There were certainly flaws in the implementation, but I still think the idea is very sound.
X1 Isle of Dread (levels 4-7) and B10 Night's Dark Terror (levels 2-4) are both great examples of how the focus on wilderness exploration dramatically changes the gameplay experience from "dungeon crawling from one encounter to the next."
Many higher-level adventures from the TSR era still ended up being of the "visit a site and fight monsters" variety, but there are three that still stand out to me today as providing an example of how high level D&D could play out:
X10 Red Arrow, Black Shield (levels 10-14) featured an invasion of the "Known World" nations by the Master of the Desert Nomads. The war is not simply a background plot in this adventure, but is played out on the map using the War Machine rules. Each of the nations has the potential to side with either the Master or oppose him, depending on the PCs' actions. The adventure plays out over the course of many months as the war progresses, and in the end the political map will likely be very different.
CM1 Test of the Warlords (levels 25+) showcases the domain rules of the Companion Set. A new king has established himself in a land north of the "Known World" that has until now been unclaimed. The PCs can pledge allegiance to this new king and establish their own dominions in this untamed land. The module is a loose framework that features a number of events that take place over the span of several years, including potentially wedding one of the PCs to the new king.
M5 Talons of Night (levels 20-25) has the PCs traveling between worlds (including a cubic world, and another one that is a tiny toy version of their own), leading armies into battle, and ultimately negotiating peace between the world's two most powerful empires (or failing, plunging the world into a massive war).
Both X10 and CM1 need a lot of fleshing out to make them playable, and each contains scenarios that are very contrived or implausible. But they provide great frameworks for paragon-tier campaign arcs. All three are good examples of adventures with higher stakes that don't simply focus on fighting tougher monsters in more dangerous locales.
It was this overall campaign structure of BECMI that I was really hoping to see in 4e when they were first talking about the three tiers of play. I love the idea of the heroic/paragon/epic structure and how each tier would have a visible effect on how the game played. I love the idea of saving much of the world-affecting magic for the paragon and epic tiers. I love the idea of paragon paths and epic destinies that reinforced your characters' roles in the narrative. It sounded like a more structured and refined take on BECMI.