The title is very intentional, for the historical minded.
This is the latest Essentials preview. And kudos to a couple of "chuckleheads" off-site, for finding it ... http://www.wizards.com/dnd/Article.aspx?x=dnd/dramp/20100723
It says: " ... The Essentials products are fully compatible with all other DUNGEONS & DRAGONS roleplaying game products, from Player’s Handbook to new products releasing in 2011 and beyond ... "
If you re-read it, it refers to "all" and "D&D" without qualifying which edition is being talked about.
Not just 4e is fair game. 3.5e is fair game. So is 3.0e, and 2e. Heck throw in a little 1e or OD&D too.
This is crazy good fun.
I know it's T.O. That's freakin' obvious. Examples:
Khan will like that 4e Sarrukhs get some tricky super high level rituals to do in FRCG. So then they use 3.5e stuff.
That's every monster power + every ppath and epicD ability ... slowly.
Sigma will like that 4e Swarm Druids can take 3.5e Dark Speech feat.
That's 30th+ level Sorc casting, super high int and cha, every feat in the game, etc ...
I'm partial to 4e Cranium Rat Swarm plus 3e style Int based abilities.
3e Leadership is just one feat ; for a 4e build that's like nothing
4e Kobolds can take one 3.5e feat, and then take 4e Epic feats.
I wonder how many Psi powerpoints can be stuffed in?
I wonder how Psiotheurgist feats work?