The Monstrous Compendium
Monster Manual 1-3 with the ability to print out single sheet monsters, like the old 2E MC should have been done. Choose your monster. Choose which illustration you want for it (Do I want the Wayne Reynolds troll or this other one here; 'none' is also a choice for illustration), choose single or multiple page, condensed or expanded format, classic stat block or new encounter presentation, etc.
Notice all the choices I have, there. That segues into something else that will cause me to give up my cash to WoTC:
Convenience
Let's assume there will be articles, adventures, NPC"s, monsters, treasures, etc along with the types of articles we've been seeing so far. These need to be presented in a number of different formats.
Let's assume that we have the Digital Dragon and Digital Dungeon. I should be able to have the Table of Contents page show me new articles, of course, along with their publish date, author, etc. I should be able to see all articles by a certain author within a certain timeframe. All articles from a certain column. All articles within a date range.
Tagging and indexing all articles is a must. Tagging, because I want to be able to say 'show me all articles dealing with trolls in 2008' and have it show me articles that actually dealt with trolls in some means, rather than just mention the monster. Especially important would be NPC's, new monsters, new spells (tagged by the various things you can ag spells for already; I should be able to search for 'all 5th level cleric spells with the [Evil] descriptor published in 2010', etc), and stuff like that. If I know that such and such adventure had a drow NPC, then 'show me all drow npc's in adventures between 10-01-2009 and 03-20-10' should pull up that adventure.
I've wasted who knows how many hours looking for things like that, even with indexes available online. If I'm paying monthly for that content as well as continued access to it, I'd better never waste even more hours when that work should be done up-front.