It's been interesting as I have had multiple opportunities to use the OLCI and standby for a flight on the day prior to my actual ticket but within the 24 hour window.

I have then on 3 separate occasions just gone to the airport the day before my scheduled flight and explained the online process and been able to standby for a flight.

I then had one bad experience after all of these where agents acted like I was crazy and that this was not allowed where I was not allowed to board. It took so long to explain and I was so upset about the situation I canceled the ticket and booked myself on a UA PDX-SEA flight. It was one of the few times I questioned my allegiance...lol