I tagged along with everybody who watched Drrr during the time it was still airing and I found the ending really terrible. Now that I've decided to rewatch it, (just finished it actually) I found the ending actually good and fits the atmosphere for such an open ended story. I wasn't able to appreciate how the ending was during the 1st watch but I guess after that conflicting emotions of the three, and seeing them reconcile right at that moment they met was just enough to convince me that I'm witnessing how a real friendship unfold right before my eyes.
After all that heavy and dark atmosphere in the story, we're left with a calm (perhaps?) ending. And, It was great to see that the views of the characters in the end of the story drastically changed (the three protagonists). I also just like how Mikado phrased his epilogue for the Dollars.
There's one thing I learned. The Dollars are the town, itself. A lot of people arrive, and a lot of people leave, never in the same colors. Something is always happening. People are hating each other, loving each other, becoming friends, and drifting apart. In the same way a town exists, so long as there are people, the Dollars will continue to exist. - Mikado, Ryuugamine