I almost always book separate nights even when the price is the same for each night. I like the flexibility of being able to cancel a night without buggering up the whole trip. I've never had to check in and out each night or even change rooms. Extra nights might mess up an upgrade given for the first night but since I am about 0/zillion on upgrades that doesn't concern me. The only pain is getting your final bill...let's just say scrutinize it big-time.