It's been a bad summer for Florida service timekeeping. The Silver Star and Silver Meteor used to be fairly reliable performers, but with CSX trackwork, traffic (freight) congestion, and now Hialeah maintenance shops seeming inability to dispatch a train on time, things haven't been so good lately. Still, these trains are most certainly NOT always late at Orlando, and the delays that do occur usually aren't too severe. I wish I could say you're unlikely to encounter delays, but you probably will right now. However, you are pretty unlikely to have any delay of more than 2-3 hours total (today's Star was 3 hours 6 minutes late at Orlando).
July On-time Performance was 7.8% for Florida trains (except Auto-Train), though that's a bit misleading. That figure only refers to trains reaching their final destination (in this case, Miami). Up at Orlando, the train could have been even later and made up time, or even early at that point only to lose time south of Central Florida. Really, there is such padding in the schedule that trains ought to nearly always be early at Orlando, but don't get me started!