Battambang is a city you stop at for 3 days and keep on moving. There's the old train track, a temple area about 40 mins from the city, and 3 good restaurants (Pizza, Eden, and an Asia Fusion restaurant) and a lot of street food. Asides from that there is a museum of local artists.

If you go from Siem Reap to Phnom Penh, spend a couple of nights here. You won't regret it. However, it's not a place you spend a lot of time at.