I'm sure I'll vent some of my issues with it throughout the next few blog posts. However, Hoi An is lovely.
I was there for three nights last week and it's so chilled I could have stayed there for a week. It's an architectural treasure trove, with buildings of Vietnamese, Chinese, Japanese and European styles, and sits along the banks of a river. It's famous for its silks and tailoring, the wonderful Japanese Covered Bridge, and its nighttime views of the lights over the water. I made sure I was there for the full moon, because you can buy paper lanterns and float them down the river for good luck. It's a beautiful sight. The hostel I stayed at was really cool (Saclo Homestay), and the owner Lena took everyone into town and recommended a place for dinner. I met some really cool people who I later met up with in northern Vietnam. If you can find it, the restaurant she recommended was Bale Well, an all you can eat affair for 110,000VND, where they literally hand-fed us for the first few spring rolls they were showing us how to make. The atmosphere was great, and we were all stuffed.
The weather wasn't ideal when I was there, but there are beaches about 4km from the town centre, and offshore islands you can easily get to by bicycle (most places rent them out for $1/day).
Hoi An is quite expensive for Vietnam, and Vietnam is an expensive country compared to the rest of SE Asia. But I found it absolutely worth it. One guy I met was there for a week, and it's a tiny place. Just with a really calm atmosphere that the bigger cities here are sorely lacking.