I've had my Keurig for a year, and will never look back. A godsend.
Emeril's Big Easy Bold
Newman's Own Special Blend
Starbucks Breakfast Blend
I like a certain amount of dark roast, but mostly love a regular roast and blend -- black, and no flavors, please, though I do enjoy a little cinnamon in coffee now and then.
Through several months of experimenting with different coffees, I found the challenge with the Keurig to be getting a strong enough cup. There were many selections for which even the small (6-oz.) size wouldn't deliver.
The four I've listed provide a satisfying strength, for my taste, on the medium (8-oz.) size. Special kudos goes to Starbucks because theirs can go large and still taste like good coffee as opposed to flavored hot water. Dunkin' recommends the 8-oz. setting for keeping the flavor as close as possible to their original, and I completely agreed with that.