Shanghai can offer something to everyone. Modern cosmopolitan city with lots of historical parts . International cuisine, vibrant art scene.. you name it!
Loved everything about Shanghai. Very nice scenery at night and The Bund is a must to see.
Shanghai makes for a great introduction to mainland China. Although it can still be overwhelming, it's easier to get around more western Shanghai -- while still absorbing so much Chinese culture and history -- than in other parts of the country. Make sure you see the French Concession area, and enjoy some xiao long bao!
I've been to Shanghai four times, for thee-day weekends when I lived in Beijing. I went there to visit Disneyland, and loved staying at a hotel called the Home Inn (Kangqiao Xiuyan Road Metro Station) 如家快捷酒店（上海康桥秀沿路地铁站店）（原秀沿路工业园区店） because it was affordable, close to the park, and lets foreigners stay there.