I mean...it gives me some idea of frequency and delays. I'm with
@T3G - if I'm at a station, the overhead LCDs can tell me what's happening on the current line. Pedestal LCDs on the platform can give more system-wide information.
Also, I will say that I loathe the TTC's displays with CP24 on them. For displays done dramatically better, the ones the MTA uses are worlds better. They say the delays happening on all lines (in big text), they often have a system map, and they have the next train arrivals. Downside: a number of them have been vandalized, but they're surprisingly tough.