I used to check-in online so I can get my room that I want reserved from the list of available rooms. But I do not do this anymore after knowing the room that I pick might not be the best room for that property. Also, sometimes the agent in the morning could assign you a different (better) room than the one the system pick automatically. For example, I got a PH suite upgrade last night. But if I did check-in online, I will get an executive room. Most front desk (that I experience with) go with the room you have selected already and do not offer you even if you can get a better room.