Raith5
Adventurer
The WotC site was having problems reading my post, so I'll share my thoughts here:
I'd like to challenge the framework of how tiers are divided. Since this is a Wandering Monster article, why not look at the monsters as a tier defining feature?
Spell access is certainly a useful feature, but I wouldn't say it is what defines a tier.
BECMI organized it around "scale of exploration" (dungeon > wilderness > city > kingdom > planes & gods). The rules that opened up thru BECMI showed that something new was happening - they really defined the tiers. Of course, the much loved Planewcape challenged those assumptions by putting low-level PCs out in the planes. And even BECMI adventures were mixed, so you'd have dungeons at Expert-tier for example.
I agree that a focus on monsters is as important to tiers as a world and story building device. And this means that they have think about where creatures like Giants and Demons etc are in terms of hit dice/level.
However I still reckon they are trying to fit a hell of a lot of content into 20 levels. I like epic type of play and would prefer more than 3 levels (though 10 levels in 4th was too much). I would rather see this stretch out to 30 levels (with faster progression) with five tiers of play or something like that.