The Trinity Railway Express, 17 years old and what Star-Telegram transportation writer Gordon Dickson refers to as a “mature” commuter rail line, is blessed with the kind of complaints from its riders that some other consumer-service operations would love to have.The riders want more of what the TRE is offering. Primarily, they want more cars so they’ll have more places to sit during rush-hour rides, and they want more trains so they can catch one more conveniently during the middle of the day.Notice that there are no complaints about the trains between Fort Worth and Dallas not running on time. There are no complaints about surly attendants or other bad service. Nobody is seriously saying the price is too high.For commuters, the TRE delivers a quality product with trains that meet their scheduled arrival and departure times at a price that easily beats the cost of parking in either of the downtown areas it primarily serves. Future commuter rail lines planned for Tarrant County should do so well.The rush-hour trains, mostly those headed toward Dallas in the morning or toward Fort Worth in the evening, are often crowded. The owners of the service, the Fort Worth Transportation Authority (the T) and Dallas Area Rapid Transit, should consider adding cars to key trains.It’s difficult to agree that the TRE should add midday trains. There may be times when there would be enough excursion riders to justify the cost, but it’s questionable.Excursion riders should know that there’s no reason to show up at the station and wait a long time for the next train. Better to check the schedule online, arrive comfortably early and be on your way.The TRE has added rider amenities. Its free Wi-Fi service might be a bit slower than that at Starbucks, but after all, it’s a moving target for electronic signals.The recently added ability to buy train tickets and passes via smartphone has had a couple of startup hiccups, but it’s tremendously convenient for commuters who are used to arriving at the platform just as the train pulls to a stop, with no time left to visit the ticket kiosk.It’s quick and easy to pay for the ride on a smartphone while you’re riding.Paying for the TRE is on the honor system, but getting caught without a ticket during random checks can be financially painful.A marketing push might boost TRE ridership, which has fallen from its 2009 peak. More of a good thing couldn’t hurt.