When I took the CS southbound a couple of weeks ago, we got to see the shorline the whole way south, and were about half an hour late the whole time. So it should be fine if you stay on time all the way.
I rode it northbound once and we kept falling behind schedule so that most of the ride north of San Francisco came in the daytime. We eventually fell about ten or twelve hours behind schedule and ended being bussed from Portland to Seattle as they turned the train in Portland. The daytime scenery around Mt. Hood was great but the bus ride around four in the morning was not so great. Especially when you had to vacate your nice cozy sleeper.