I have a Mountain Hardware bag with Thermic Micro insulation. It's as light as down for the same temp rating, and just about as compressible. If I'm expecting lots of wet conditions that's the bag I go with, otherwise I have a couple down bags I choose from depending on temperature.

That Marmot Arroyo looks like a great bag, excellent choice if you go with down. With a 30 degree rating, I wouldn't think it is too warm.