Love the dragon articles, haven't done much other than mine the dungeon articles.
The compendium has been invaluable!! I look up what I need, copy it into a dual-column word file and header it with the encounter name, footer it with Xp & loot and voila! It makes editing monsters sweet and easy. My entire game has only humans and Yuan-Ti in it. As it turns out, a few changes to a Succubus and you have a Yuan-Ti snake Charmer that works perfectly. Using the word file I can save these creatures for future use, as well.
I don't know about using the compendium "during" a session since I don't need it. With the GM Screen and my word notes, I am now 100% pc free while running the game.
With the compendium it takes me less than 10 minutes to put together my battles. Just 'cos I know you all want to know, here's my steps:
1. Decide the major badguy/theme, locate creature, copy/paste, edit to PC level.
2. Search for additional creatures (brutes, minions, skirmishers), Copy/paste, edit to PC level
3. Search for magic items & copy/paste
I spend more time working on my plot, terrain, or skill challenges thanks to the Compendium. (PS, if you have Word 2k7, set the copy default to keep only text and you'll get editable text without any background from the compendium. Makes it very nice for printing)