We've been using the Keurig exclusively for a couple of years now. At first, we bought the k-cups, and that became very expensive, so after a few months we switched to the included reusable device and grinding our own Starbucks. It's really nice since there is no wasted coffee and you get a fresh cup every time. I like to have a cup of regular first thing in the morning, then switch over to decaf.
A couple of tips for grinding your own and using the reusable filter:
Grind your coffee into almost a powder, it'll impart more flavor that way.
Use filtered softened water and it'll almost never need de-scaling.
Fill the reusable filter only half-way full, which is about the same as what the k-cups are. This is about 1 tbls of coffee. This way it will brew fast, make a flavorful cup of coffee, and you won't waste coffee. Much more than half-full and the machine will brew really slowly.