I didn't spend long in Da Nang but it's known for good food (especially seafood) and is a perfect spot to base yourself for the Hai Van Pass. It's only a short drive from Hội An and you can get a cheap bus there but be warned, they will try to overcharge you for the bus - it should be 20,000d but they will lie to you and even some of the locals might join in the lie, but don't budge!
I arrived by train late at night with a friend and we found it difficult to get a cheap guesthouse. We ended up giving in and paying more than we usually do. There are still deals to be found but it seems like the prices are higher than other areas.