For me it all depends on the time of year and the time of day I expect to be arriving. For busy seasons (summer, Christmas, Easter) it's WELL worth it to use online check-in, you're literally in and out with little to no wait.
On my trip next week (checking in October 28th) I'll be checking in at the desk. Why? It's not an overly busy time of year, it's a Thursday, and as I'm driving down and will be in Orlando for 4 days before I check-in I know I'll be arriving very early in the AM so there won't be a long line ahead of me. Like others I prefer to use the at desk check-in for a number of reasons. Checking in feels like the start of a vacation, it has it's charms like that, and you certainly do have the opportunity to discuss where your room will be (and if you want to change that) etc with the CM more then you would on an online check in.